UMER3ITY OF MONTANA BULLETIN 


BUREAU OF MINES AND METALLURGY SERIES 


NO. 3 


MECHANICAL ORE SAMPLING IN 

MONTANA 




"'A 




By H. B. PULSIFER 


STATE SCHOOL OF MINES 
BUTTE, MONTANA 

March, 1920 





THE UNIVERSITY OF MONTANA 

Edward C, Elliott, Chancellor of the University 

The University of Montana is constituted under the provisions of Chapter 92 of the 
Laws of the Thirteenth Legislative Assembly, approved March 14, 1913 (effective July 
1. 1913). 

The general control and supervision of the university are vested in the State Board 
of Education. Tire Chancellor of the University is the chief executive officer. For each 
of the component institutions there is a local executive board. 


Montana State Board of Education 


S. V. STEWART, Governor.Ex-officio, President 

S. C. FORD, Attorney General.Ex-officio 

MAY TRUMPER, Superintendent of P*ublic Instruction - , - - Ex-officio, Secretary 

W. S. HARTMAN (1920) J. B. KREMER.(1922) 

JOHN DIETRICH.(1921) LEO H. FAUST.(1923) 

A. LOUIS STONE.(1921) W. H. NYE.(1923) 

C. H. HALL.(1922) WM. M. BOLE.(1923) 


Tire University comprises the following institutions, schools and departments: 


The State University, Missoula 

Established February 17, 1893, and Consisting of 


The College of Arts and Sciences 

The School of Law 

The School of Pharmacy 

The School of Forestry 

The School of Journalism 

The School of Music 

The School of Education 

The School of Business Administration 


The Summer Quarter 

The Biolo^cal Station (Flathead Lake) 

The Public Service Division 
Special War Courses— 

Military Service Course (one year) 
Nurses’ Preparatory Course (one year) 
Office Training Course (one year) 

The Graduate Division 


Edward O. Sisson. President 


The State College of Agriculture and Mechanic Arts, Bozeman 


The College of Agriculture 
The College of Engineering 
The College of Applied Science 
The College of Household and 
Industrial Arts 

Coiu'ses for Vocational Teachers 
The School of Music 
The Summer Quarter 
The Agricultural Experiment Station 


The Agricultural Extension Service 
The Secondary Schools— 

Home Economics 
Mechanic Arts 
Agriculture 

Special War Courses— 

Military Service Course (one year) 
Nurses’ Preparatory Course (one yeax) 
Office Training Course (one year) 


Alfred Atkinson, President 


The State School of Mines, Butte 

Established February 17, 1893 

The State Bureau of Mines and Metallurgy 

Charles H. Clapp, President 

The State Normal College, Dillon 

Established February 23, 1893, and Consisting of 

The Teachers’ Certificate Course The Four-Year Course 

The Three-Year Course The Rural Teachers’ Course 

The Course for Supervisors 

Sheldon L. Davis, President 


For publications and detailed information concerning the different schools and colleges 
address the president of the particular institution concerned. Communications intended for 
the Chancellor of the University should be addressed to the State Capitol, Helena, Montana. 

















■THE WASHOE SAMPLER OP THE ANACONDA MINING COMPANY 












UNIVERSITY OF MONTANAv BULLETIN 


BUREAU OF MINES AND METALLURGY SERIES 


NO. 3 


MECHANICAL ORE SAMPLING IN 

MONTANA 








> 0 - 


By H. B. PULSIFER 




> 

j > 
) 

O ^ 


STATE SCHOOL OF MINES 
BUTTE, MONTANA 


March, 1920 




4 


MONTANA STATE BUREAU OF MINES AND METALLURGY 



STATE BUREAU OF MINES AND METAL¬ 
LURGY STAFF 


CLAPP, CHARLES H. - - - - - Director and Geology 

PhD., Massachusetts Institute of Technology, 191Q. 

ADAMT, ARTHUR E. ------- - IMining Engineer 

E. M., Montana State School of Mines, 1907. 

PULSIFER, H. B. - -- -- -- Metallurgy and Safety 

B. S., Massachusetts Institute of Technology, 1903; 


Ch. E., Armour Institute of Technology, 1915; 
M. S., University of Chicago, 1918. 


lISir^KT OF QOMQI^ 

wtetivio 

OOOUMtWTB otmib 












CONTENTS 


Page 

Introduction ..... 7 

Authorization....... 7 

^ Object.......... 7 

Acknowledgments. 7 

Purpose of sampling..... 8 

Principles of sampling. 9 

Necessary operations... 10 

Crushing and grinding....... 11 

Dividing or selecting... 12 

IMixing the sample.. 12 

Drying the sample. 17 

Cone and cpiarter sampling... 17 

Probability sampling... 19 

The largest pieces. 21 

High value minerals.. 23 

Equipment for sampling. 24 

Crushing and grinding machines. 24 

Dividing instruments.. 26 

The hand shovel. 26 

The split shovel...-. 26 

Riffle cutters. 26 

Pipe samplers... 29 

The Brunton vibratory sampler. 31 

The Brunton oscillatory sampler..... 34 

The East Butte sampler. 34 

The V^ezin sampler...-.--- 34 

The Snyder sampler. 36 

Mixing machines.-.:.A.'...v...:..'... 38 

Drying machines...-.,.—..-. 40 

Sampling of test lot by State Bureau..... 40 

IMill flow sheets.»......r.*:.. 42 

Sampling mills in IVIontana..’-'-...-.-. 46 

The Washoe Sampler...-.-. 46 

East Helena sampling mills...-. 49 

The East Butte sampling mill. 57 

Anaconda sampling mills. 60 

Sampling in Montana concentrating and cyaniding mills... 67 

Summary and conclusions.-.-. 68 

Important publications on sampling. 69 

Index..-. 










































6 


MONTANA STATE BUREAU OF MINES AND METALLURGY 


ILLUSTRATIONS 

Page 

Figure 1. The Washoe Sampler...Frontispiece 

“ 2, Stand riffle cutter. 14 

“ 3. Cone and quarter sampling—spreading... 16 

“ 4. Cone and quarter sampling—mixing. 18 

“ 5. Probability curve for sampling results. 20 

“ 6. Split shovel sampling. 25 

“ 7. Inclined table riffle... 27 

‘‘ 8. Corner of East Helena bucking room. 28 

“ 9. Pipe sampling of flotation concentrates. 30 

“ 10. Blades of Brunton vibratory sampler. 32 

“ 11. Mechanism of Brunton oscillatory sampler.— 32 

“ 12. First sampler and first rolls at Washoe Sampler. 33 

“ 13. East Butte type of sampler.. 35 

14. Vezin sampler.... 36 

“ 15. Snyder sampler. 37- 

16. Drum mixer, sampler, and rolls in East Butte mill. 39 

“ 17. Taylor and Brunton sampling system. 47 

“ 18. View of Washoe Sampler from the east. 48 

“ 19. Third cutter and third rolls in Washoe Sampler. 50 

“ 20. Unloading ore at East Helena No. 1 mill. 52 

“ 21. Sampling mill No. 1 at East Helena. 53 

‘‘ 22. First floor equipment at East Helena No. 1 mill. 54 

“ 23. Vezin sampler wings at East Helena sampling mills. 55 

24. Steel sampling floor at East Helena. 56 

25. East Butte sampling mill. 58 

26. Third sampler and third rolls in East Butte mill. 59 

27. Anaconda sampling mill. 61 

28. Diagram of Anaconda sampling mill. 62 

29. First sampler and second crusher in Anaconda mill. 63 

30. Bucking room at Anaconda sampling mill. 65 


































OBJECT 


7 


INTRODUCTION 

AUTHORIZATION 

The bill creating the Montana State Bureau of Mines and Metal¬ 
lurgy, enacted by the Legislative Assembly of Montana for 1919 
(Chapter 161, Page 311), states that it is one of the objects and 
duties of the new bureau, “To study the mining, milling, and smelting 
operations carried on in the State, with special reference tO' their 
improvement”, also, “To prepare and to publish bulletins and reports, 
with necessary illustrations and maps, which shall embrace both a 
general and detailed description of the natural resources and geology, 
mines, mills, and reduction plants of the State.” 

OBJECT 

A study of sampling and the sampling facilities of Montana is 
presented, in accordance with the above authorization, to widen and 
deepen the general knowledge relating to the common and necessary, 
yet rather technical work of sampling. It is hoped that prospectors 
and miners will benefit from the study, for their interests have been 
kept prominently in view. The sampling mills in which ore sellers 
will find personal interest have been thoroughly studied and their 
reliability tested by an expensive series of samplings to demonstrate 
their precision on an ordinary lot of ore. It is felt that even small 
advances toward the uniformity, precision, and efficiency of sampling 
mean so much to the industry as to warrant even far more effort and 
cost than is represented in^ this study. 

ACKNOWLEDGMENTS 

The managements of the American Smelting and Refining Com¬ 
pany, the Anaconda Copper Mining Company, and the East Butte 
Copper Mining Company have heartily welcomed the study and have 
assisted in every way possible. Each company has put itself to expense 
and trouble to join in the work. 

Particular acknowdedgments are due Messrs. Smith, Morse, and 
Adams of the American Smelting and Refining Company, to Messrs. 
Laist, Bender, Gillie, Margetts, and Demond of the Anaconda Copper 
Mining Company, and to Messrs. Rohn and Beaudin of the East Butte 
Copper Mining Company. The men mentioned have been personally 
helpful in forwarding and correcting the work. 

Dr. Clapp of the State Bureau has taken a strong interest in the 
work and helpfully directed the preparation of the report. 


8 


MONTANA STATE BUREAU OF MINES AND METALLURGY 


THE PURPOSE OF SAMPLING 

The sampling of a lot of ore is carried out in order to supply the 
analyst with a 4-ounce envelope of finely ground powder which, when 
selections are made in from half-gram to thirty-gram portions, shall 
give the analyst average results with a precision of about one part in 
fifty for the important components, or elements, moisture excepted. 
The usual chemical determinations are for gold, silver, copper, lead, 
zinc, sulphur, iron, silica, lime, and magnesia, and for special elements 
in particular ores. 

Sampling is thus seen to have an amazing purpose in view; to take 
from a lot of ore—be it one ton, fifty tons, or five hundred tons— 
only about thirty-two ounces of material which shall uniformly con¬ 
tain all the components of the original lot in exactly the proportions 
in which they exist in the original lot of ore. Even this final sample 
of about thirty-two ounces must be capable of division so that the 
different packets into which it is separated must be chemical duplicates 
of each other and supply seller, buyer, control analyst, smelter, and 
umpire analyst with as nearly identical results as possible. Yet, in 
spite of the enormous difficulties in practice, perfectly satisfactory 
sampling is actually attained daily. 

The lot of ore to be worked upon will likely contain very fine 
material, sandy material, and sizes up to big chunks; it will contain 
desirable minerals and undesirable rocky gangue; it may contain free 
metals, clayey gouge, and crystals in all degrees of purity. It is remark¬ 
able that the task can be done at all; it is nothing less than one of the 
great achievements of modern engineering and industry that it can be 
done easily, quickly, cheaply, and with precision. 

Ordinary sampling mills will secure a 100-pound sample from a ' 
50-ton lot of ore in from fifteen minutes to two hours, and then from 
this sample the sample man in the bucking room will produce the 
analyst’s packets of thoroughly ground, dried, and mixed pulp in 
another hour. 

The cost of sampling varies from 5 cents to $1.50 a ton, depending 
upon the amount, character of ore, and the method and equipment 
used. 

Sampling has accomplished its purpose if the small packet will 
supply the half-gram, fifteen-gram, or thirty-gram selections for the 
analyst so that he can get his results with the required precision. The 
sampling is satisfactory if the average results on different selections 
from the same packet, or on selections from different packets, or on 
selections from different samplings, agree to one part in fifty parts, 
or, as they sometimes do, to one part in one hundred parts. The pre¬ 
cision may be less with elements present in excessively small amounts, 
like gold and silver. The chemical work is subject to both constant 
and chance errors, so that single results, or too many significant 
figures in the results, have little meaning; error may come as likely 
from the analytical work as from the sampling operation. 



PRINCIPLES OF SAMPLING 


9 


Sampling has failed of its purpose if selections from packets do 
not agree within the desired limits, or if the different packets from 
the same sampling do not agree, or if packets from different samplings 
are discordant. The best test of accuracy in sampling is to resample 
or sample by another method. It is rarely cheap or practicable to 
actually extract the desired metal or attempt to separate a compound 
from an entire large lot in order to determine its amount; in such a 
case the recovery figure, instead of the composition figure, is obtained, 
because the losses which the chemist compensates for, the plant 
operator cannot avoid. 

Whoever mines ore, sells it on the results of the analysis of a 
sample; ore is purchased on its value as determined by sampling; the 
plants are operated on a basis of results from sampled materials; 
efficiencies and losses are all based on results from samplings. 
Sampling is therefore one of the most vital and necessary operations 
of modern mining and metallurgical industry. 


PRINCIPLES OF SAMPLING 

*Woodbridge in a recent paper published by the United States 
Bureau of Mines defines sampling as follows: “The correct sampling 
of a lot of ore is the process of obtaining from it a smaller quantity 
that contains, in unclianged percentages, all the constituents of the 
original lot.” He further qualifies and defines the operations in his 
next paragraph: “The commercial object of sampling is accomplished 
when the ultimate sample obtained meets the above conditions within 
an allowable limit of error, and has been obtained with reasonable 
speed .and at a moderate cost. The final sample should be dry and of 
such bulk and degree of fineness as to be immediately available for 
the determination by the assayer or chemist of one or more of its 
constituents.” 


THE OPERATIONS OF SAMPLING 

Four wholly different, yet essential, sorts of work may be done to 
accomplish the intended purpose of sampling. The four operations are: 

1. Crushing, or grinding. 

2. Selecting—dividing or cutting. 

3. Mixing. 

4. Drying. 

These essential operations are carried through to varying degrees 
and in whatever order the conditions require. Thus, with flotation 


*Woodbridge, J. T.; U. S. Bureau of Mines, Technical Paper 86 (1916). 




10 


MONTANA STATE BUREAU OF MINES AND METALLURGY 


concentrates, which are already finely ground and well mixed in pro¬ 
duction, the work is largely in cutting out numerous selections, drying, 
regrinding the lumps made by the drying, mixing the pulp, and 
dividing it between the several packets. A lot of coarse, rocky ore 
may be dry and excessively hard; in this case the work is mostly 
crushing and selecting until the small final portion is dried, finely 
ground, mixed, and split for the assayers’ packets. 

Successful sampling demands that a rational sequence be followed 
and that attention be continuall}^ give to certain fundamental con¬ 
ditions, explained later, lest some slip or unexpected influence vitiate 
the entire work. It is self-evident that the final result cannot be more 
perfect than the most imperfect step in the sequence; if six divisions 
are made, and one is imperfectl}'' done, perfect work in the other five 
does not compensate. 

Sampling can frequently be accomplished by different methods or 
by changing the sequence of the steps; one usually uses the method 
most feasible or least costly. Thus, if one had a 50-ton lot of lump 
ore to sample, an imaginary way to get the required results might be 
to dry the entire lot, then grind it to pass 100 mesh, then mix it 
thoroughly, then at last take out just enough of the dried, ground, 
and mixed ore to fill the sample packets. For most metallurgical 
purposes the cost of such an operation would be absolutely prohib¬ 
itive; the nearest commercial approach to it is probably the sampling 
of the Cobalt native silver ores. The usual western practice with lump 
ores is to crush to 2- or 3-inch size, select a fifth and crush it finer, 
select a fifth and crush it again; and this sequence is repeated, two, 
three, four, or more, times, until a small amount is obtained which 
alone is dried, finely ground, mixed, and distributed between the 
packets. 

The method of making the entire lot uniform and then selecting 
a few duplicate portions for the analyst is attractive for the ease and 
simplicity of the few selections involved. In addition, this method is 
one which may come into use more and more on account of the lines 
along which metallurgy and industrial chemistry are advancing. Pipe 
sampling of concentrates is almost an example of this simple method. 
In fact, this method is actually followed in the most approved manner 
of sampling lead bullion. A kettle of molten lead ready for casting 
into bars is stirred for 15 minutes; as the stirring continues the 
sampler inserts a steel rod, with a row of conical depressions in it. 
On the withdrawal of the rod each little cone of lead, which fills a 
depression, will come out of the kettle of the proper weight for the 
assayer and will contain the correct proportions of all components 
of the kettle of molten lead. Two lots of 7 little cones, all from the 
same kettle, were cupelled, and the following results were obtained: 


CIUTSHING AND GRINDING 


11 


Series No. 1 


Series No. 2 


Gold Silver 

.30 oz. 81.7 ozs. 


Gold Silver 

.30 oz. 82.1 ozs. 


.30 82.0 

.30 81.4 

.30 82.3 

.32 82.1 

.30 82.0 

.30 82.3 


.30 82.4 

.30 82.0 

.30 81.7 

.30 82.0 

.30 82.0 

.32 81.8 

.30 82.0 


Average: .30 82.0 


1 his method of sampling lead bullion has given eminently satis¬ 
factory results at a tri\'ial cost. Pipe sampling of a pile, or carload 
of concentrates, is also a matter of very slight cost and will necessarily 
give correct results if the lot is uniform. Sampling by taking a few 
small portions from a uniform lot of fine material, either during its 
production or after it is in a batch, is a method which should always 
be borne in mind; and if the proper condition for this is to araise 
during the treatment of aii}^ material, sampling can be profitably 
delayed until that stage is reached. Unfortunately, the producer of 
ore seldom has his material in a fine and uniform condition suitable 
for such sampling. 

Crushing and Grinding.—The crushing of ore for sampling pur¬ 
poses is largely a matter of mechanics, power, and capital outlay. It 
usually does no harm if some of the material is finely divided during 
the course of crushing the larger pieces to the necessary dimensions. 
Since a great variety of sizes will inevitably be produced, the making 
of fines increases the number of particles and favors the sampling 
when it is done on the probability basis. 

Many of the crushing machines on the market are excellent for 
reducing ore sizes and fulfil most of the expected functions. Capital 
outlay is always a serious consideration and machines are primarily 
installed on their gross capacities and not on the basis of how thor¬ 
oughly they wdll accomplish the crushing task. Sampling mills do 
have a strong claim for heavy and pow^erful machinery, since an 
unusually large or tough piece of rock slipping through one machine 
may spoil the sampling because of its excessive mass and one-sided 
composition. In ordinary ore-dressing practice it means little if slabs 
fall through machines or if large rocks spring the rolls and fail to be 
w'ell crushed. Ultimately the pieces will be caught and crushed or 
returned to the first crushers by the sizing devices. But most sampling 
mills do not have sizing devices and it is possible for large pieces to 
get into the sample. It is not uncommon to find a sample which, 
although 90 to 99 per cent, is properly sized, contains a few unduly 
large pieces, thus tending to vitiate the results. 

Several methods may he proposed for overcoming the sizing dif¬ 
ficulty. The idea of using very heavy rolls is neither new nor impres- 


12 


MONTANA STATE BUREAU OF MINES AND METALLURGY 


sive. Dodge type crushers, which make a finer product than the Blake 
type, would be only a partial remedy. There appears to be a field for 
a type of crushing machine which shall be so constructed as to make 
the passing of thin slabs impossible; capacity could be somewhat 
sacrificed for the sake of the sizing feature. 

In regard to grinding the finest sizes for the final pulp there 
appears to be an open field for studying the correlation of grinding 
substance with the work accomplished. A complete study of this 
detail of sampling and grinding should include the composition, 
structure, and physical properties of the grinding substance. One 
important factor would be to accurately determine how much of the 
grinding substance is abraded to contaminate the sample. 

Dividing or Selecting. —The phrase, “selecting the sample,” could 
well be replaced with the words, “dividing the lot,” for the idea 
inherent in SELECT is that a division is made which is based on some 
property or cjuality of the jDortions available. The word select is 
always used in this paper with the simple meaning of divide. The 
most vital principle in any and all sampling is that division shallHiot 
be dependent on any quality of the parts. Whether one is removing a 
small portion of a perfectly mixed lot, or Avhether one is making a 
thousand mechanical divisions, the separation demands the absence 
of discrimination. 

Mechanical sampling attains its best precision with well-designed 
equipment which allows no division based on a property of parts, as 
on the coloring, the sizes, or the relative densities of the ore pieces. 
If a piece of machinery is to handle pieces of rock several inches 
across just as impartially as it handles quarter-inch sizes it probably 
means surprisingly large equipment. When confronted with the prob¬ 
lem of sampling very large pieces, the engineer sometimes decides 
to crush enough to accommodate the sampling machinery; he rarely 
builds ungainly machinery, but he frequently handles large sizes with 
too small machiner 3 \ To the mechanical engineer a compromise is a 
“practical” solution of the problem, but to the mining engineer a 
compromise involving even slight deviations from impartial sampling 
is a perversion of the whole function. 

The precision of modern mechanical sampling, as based on the law 
of probability brought into play by hundreds and thousands of divi¬ 
sions, is a source of much pride and satisfaction to the engineers and 
men interested. The demonstrations to he presented in later para¬ 
graphs will substantiate this opinion and establish a confidence in the 
practice. Mechanical cutters in the mills, and riffle dividers in the 
bucking rooms, allow ores to be sampled without possibility of being 
influenced either by human craft or stupidity. Also, fortunately, both 
speed and cheapness are in favor of wholly mechanical sampling. 

Mixing the Sample. —The mixing of a large lot of ore consisting of 
large and small pieces is almost impossible and, besides, is wholly 


MIXING THE SAMPLE 


13 


useless. W hen you try to do this you find that any method of hand¬ 
ling assorted sizes allov/s segregation if the material is dropped, or 
let roll, or even moved by ordinary implements. The material cannot 
be properly sampled by small selections of single pieces, because the 
larger pieces exceed the proportionate composition in all components. 

The mixing of large lots of fine ore or mill products is not as 
difficult an operation - as the preceding, but is seldom practicable 
unless done incidentally to the production or transfer of the material. 
Even if a lot of fine ore appears to he uniformly mixed there is no 
easy demonstration of the fact, and it is much safer to depend on a 
considerable number of cuttings. The frecjuent division of a fairly 
uniform material is carried out in practice when mill streams are 
sampled, either mechanically or by hand, when cars and bins of con¬ 
centrates are pipe sampled, and in shovel sampling by the tenth- or 
fifth-shovel method. The three instances last mentioned are really 
applications of probability sampling, but probability sampling used 
where the material is known to be nearly uniform, and where from 
50 to 500 selections suffice to establish the required precision in the 
sample. 

A thorough mixing of the final portion of pulp previous to its 
division between the several packets is indispensable. A large number 
of rollings on a suitable cloth or paper is the almost universal way 
to do the final pulp mixing. Rolling, when skilfully done, accom¬ 
plishes the purpose, but the great objection to rolling is that it is 
tedious and requires both time and patience. If a cloth fabric is used 
it may well have a pebble-grained surface; a paper should have a 
matte surface. The surfaces of either fabric or paper are commonly 
colored black to show the sample more easily. 

Substitutes for rolling the pulp on cloth or paper have been pro¬ 
posed; the Anaconda sample mills use cube mixers and at the School 
of Mines a small table riffle answers the purpose. At Anaconda 
both mills are equipped with 8-inch cube mixers which rotate by 
power and slowly enough for the contents to undergo practically 
the same sort of tumbling which a pulp would get when rolled on a 
fabric. Cube mixers have not proved satisfactory in all cases and 
their use in the State is limited to the Anaconda mills. Classes in 
assaying at the School of Mines have recently mixed their final pulps 
by pouring them, with shakings to and fro, at least ten times through 
a table riffle. As far as can be determined in the the course of the 
regular assaying work, the riffle mixing is fully adequate and will 
be explained in considerable detail. 

A riffle cutter may be used to make either a very few or a greater, 
and almost unlimited, number of cuts during the division of an ore 
sample. Figure 2 shows an operator pouring a sample through a 
riffle cutter which has 26 slots. When the sample container rests 
on the edge of the cutter, and the material is merely allowed to flow 
through the 12 slots which extend the width of the ore stream. 


14 


MONTANA STATE BUREAU OF MINES AND METALLURGY 



FIG. 2.—STAND KIPFDE CUTTER USED AT THE STATE SCHOOL 

OF MINES. 

The culter has 2G, 5/a-inch slots, and is intended for dividing S-mesh 

stock. 



MIXING THE SAMPLE 


15 


there will be 6 streams of ore flowing into the sample half, and the 
lot may be said to be cut 6 times for sample. When the operator 
moves the container across the top of the riffle, say 20 times during 
the pouring, all of the slots are brought into play and the lot may be 
cut 20x13, or 260, times for sample. The operator might, however, take 
the ore from the container in a scoop and then pour it through in 
small portions, shaking each scoopful 20 times across the riffle. If the 
operator takes a lot of ore in 10 scoopfuls, and pours each across the 
26 slots, with 20' to and fro motions, he makes, altogether, 10x13x20, 
or 2,600 cuts, for the sample. 

It is thus seen that a lot of ore is very easily cut into a larger 
number of portions by merely shaking the ore stream across the 
riffle. When the two halves of the divided sample have been united 
the lot of ore has been thoroughly mixed. Both gross and minute 
inequalities are dispersed throughout the sample by cutting and 
uniting several times, in other words, the lot has become unusually 
“well mixed.” 

The author is of the opinion, that, if a lot of sample pulp is shaken 
10 times across a riffle, which makes 1,000 cuts for sample each time, 
the united pulp will be as well mixed as by rolling 1,000 times on a 
cloth. The riffle mixing can be done in less than 5 minutes, while the 
rolling will rarely require less than 15 minutes. 

In order to make an exacting test of the mixing that can be done 
with a riffle the author prepared 500 grams of quartz and 500 grams 
of iron ore by grinding each and passing them through a 100-mesh 
sieve. Each lot was, of course, dry and thoroughly mixed. The iron 
ore was poured over the quartz in a pan and then the material was 
poured through a 12-slot riffle giving nearly 100 shakes during the 
30 seconds required for the powder to flow from the pan. Two grab 
samples of about half-gram size were taken on a spatula from each 
half. The two portions were united and the operation repeated. This 
was done 7 times and each time two grab samples from each half 
were taken for analysis. The chemical results were as follows: 

Quartz, 3.17% iron; iron ore, 43.78% iron; average, 23.48% iron. 

PERCENTAGE OF IRON IN GRAB SAMPLES 


Ave. Deviation 

j\Iixing The Four Samples Average from 23.48 

1st .15.72 32.72 6.04 30.80 21.32 10.44 

2nd .20.24 20.12 19.24 21.12 20.18 3.30 

3rd ......20.12 21.40 23.40 22.88 21.95 1.51 

4th .23.28 23.50 , y23.40 23.20 23.34 .15 

5th .23.64 q 23,64:t "23.44 23.64 23.61 - .13 

6th . 23.56 . 23.64 ' 23.44. 23.64 23.57 .11 

7th .23.36 23.44 23.52 : 23.64 , 23.49 ' '.09' 


The chemical analyses show that the first mixing had intermixed 
the iron ore and quartz to a very considerable extent, although far 









1() 


MONTANA STATK BUliEAU OF MINES AND METALLURGY 



FIG. 3.—CONE AND QUAKTEH SAMPIANG. 

The cone has heeii formed over a wooden cross and the men are just hej^innin^ to spread the pile. 











DRYING THE SAMPLE 


17 


from enough to be utilized. The second mixing adjusted the compo¬ 
sition to within a few per cent, of what it should be. The third mixing 
brought practically perfect final composition in streaks, while the 
fourth mixing doubtless rendered the entire batch homogeneous to 
within 1 part in 100 parts, which is of the order of the chemical 
analyses, themselves. The 5th, 6th, and 7th mixings changed the com¬ 
position in an almost inappreciable degree. The chemical determin¬ 
ation of iron was chosen because it could be done more easily and 
with greater precision than almost any other determination or assay. 

Alaterial which yields identical composition on haphazard samples 
fulfills the test of uniformity, in this instance rather a test of the 
mixing than anything else. 

Whenever the riffle cutter has been tested under proper conditions 
it has given admirable results; it is, accordingly, strongly recom¬ 
mended wherever it can be used. The prospector and miner will find 
riffles both cheap and handy. Riffles can be used wherever cone and' 
quarter sampling or split shovel sampling is now used. The utmost 
use of riffles will tend toward uniformity, low cost, rapidity, and the 
greatest possible precision in sampling. 

Drying the Sample. —Two devices are in common use in Montana 
for dr 3 dng ore samples; the most common is the cabinet shelf dryer, 
heated by steam or electricity; steam tables with large flat tops are 
also found at most mills. The shelves of the cabinet dryers will accom¬ 
modate pans large enough to hold eight or ten pounds of ore in a thin 
layer. Larger samples are divided among pans or spread on the steam 
table. An hour’s drying is usually considered enough, although the 
sample may be left in the dryer much longer while awaiting its turn 
for fine grinding. 

Drying is by far the simplest and easiest of the four mechanical 
operations in ore sampling. 

The drying problem, if indeed there is any, is rather one of pro¬ 
curing a sample to dry, or taking the moisture sample, then drying 
the sample after it is procured. At some ^Montana mills the sample 
for moisture is a composite made up of several cuttings from different 
places well within the lot, at other mills a somewhat arbitrary cor¬ 
rection is made to the moisture on the regular mill sample, or on a 
portion of the last mill crushings. How to get a moisture sample 
cheaply and accurately is the same sort of problem as how to cheaply 
and accurately sample spotty gold ore; both are troublesome. 

CONE AND QUARTER SAMPLING 

There is a method for sampling ores, handed down through many 
decades, which is known as the cone and quarter process and is sup¬ 
posed to have originated in Cornwall. The ore is thrown into a 
conical pilCj which is then spread out with a tool as the operator 




18 


MONTANA STATE BUREAU OF MINES AND METALLURGY 



fig. 4.—CONE AND QUARTER SA3IPUING. 

The first cone is being ringed to mix the fine, damp material. 



PROBABILITY SAMPLING 


19 


circles about the pile. Quarters are marked and two opposite ones are 
shoveled away, leaving one-half of the original lot as a sample. The 
coning and quartering is repeated as often as necessary to get the 
right-sized sample. Figure 3 shows the operation in progress on a 
steel sampling floor. 

The principle involved in cone and quarter sampling is that of 
symmetry about a vertical axis; an additional and less effective 
principle is that of compensation of opposite quarters. The idea in 
the cone and quarter method is that the ideal pile shall be uniform 
about the center, but, if the pile is not uniform, the opposite sectors 
across any given diameter may be expected to compensate for each 
other and so establish a working average. The method of dividing the 
lot allows the principle of diagonal compensation to apply to both 
sample and discard. 

Although splendid work can be done by the cone and quarter 
method the principles are not as simple nor is the work as independent 
of human discrimination as sampling by other methods. An exag¬ 
gerated segregation of fine and coarse particles always occurs during 
the coning of the pile; depending entirely on the ensuing distribution 
of the finer core of the pile, there may be either a fair halving or a pre¬ 
ponderance of values in either sample or reject. Mixing the lot by 
‘Tinging about” before coning is a common practice (see Figure 4). 
The use of crosses to help center the pile and hold the sides during 
the division is also common practice. 

PROBABILITY SAMPLING 

The law of averages and the theory of probability demonstrate 
that if either single pieces or small portions of a large lot are chosen 
at random the composition of the selection will approach, after 
enough selections and as a limiting condition, the composition of the 
entire lot. Obviously, if one selects the entire lot, the sample and lot 
become identical. However, it is not necessary to take the entire lot, 
for by mixing and taking a sufficient number of single particles, or* 
by making enough cuttings, or by a combination of mixing and 
dividing, it is possible to take not more than one-fifth, one-tenth, or 
even one-twentieth of the lot and still get a truly representative 
sample. Shovel sampling, split shovel sampling, riffle sampling, and 
all types of mechanical cutters involve more or less of the proba¬ 
bility principle. 

To make the probability overwhelmingly on the side of pre¬ 
cision, a questionable number of divisions is not taken, but thousands 
of divisions, each portion containing thousands of particles, are com¬ 
monly made. Furthermore, the possibility of large pieces influencing 
the results is precluded, and any influence that can interfere with 
absolutely random division is avoided. Thus any influence which tends 
to select according to size, weight, shape, density, color, hardness, 
porosity, or any other imaginable property is eliminated. 


Number of Cuttings for Sample 


20 


MONTANA STATE BUREAU OF MINES AND METALLUBCY 


Actual 

Lead 

Content 



Percentage of Lead in Sample Selected 


FIO. 5.—PHOHAl*lLlTY ( I UVK FOU DISTHIlIl TI()\ 
OF SA3IPL1.\'(; RKSriiTS. 






















































































































































































































































































































































































































































































































TIIK LARGEST PIECES 


21 


There is no doubt but that the results of sampling must follow 
some probability curve, mathematically determinable by the factors 
and quantities involved; the engineer makes certain that the curve 
shall be of the shape indicated in Figure 5. The curve means that, 
depending on the number of divisions or cuttings for sample, the 
probable result will lie within the extremely narrow, vertical portion 
of the blackened area. On this basis, if one repeatedly crushes between 
divisions so as to circumvent the influence of large single particles, 
the limit of accuracy is not exceeded, although the crushing and 
dividing is repeated as many times as neessary to sufficiently reduce 
the size of the sample. 

In actual samiiling the sequence of crushing and cutting is com¬ 
monly performed from six to ten times. Each portion of the thousand 
or more selections made by one machine contains millions of particles 
and the final result has every assurance of correctness and is capable 
of proof. The proof consists, not in analyzing the entire lot, which, 
as already stated, is impossible, but in repeating the process, in getting 
duplicate samples, or by sampling by an entirely different method. 

If a lot of ore weighing 50 tons requires 60 minutes to go through 
a mill whose mechanical cutters are taking out a fifth at the rate of 
60 cuts a minute and are in series of four, the first cutter will make 
3,600 selections and take out 10 tons containing millions of particles. 
After crushing, the second cutter will make its 3,600 selections from 
the first sample and take out its 2 tons containing again millions of 
particles. Then the third cutter will divide the 2-ton lot, making its 
3,600 selections and taking out 800 pounds containing again some 
millions of particles. The last cutter will divide the 800 pounds and 
with its 3,600 selections take out 160 pounds in another sample like¬ 
wise containing millions of particles. The process of crushing and 
dividing is then continued with suitable machines, and usually in the 
bucking room, until the final analysts’ packets, each containing millions 
of particles, represents the original lot with the same precision as 
that of any previous larger selection or sample. 

THE LARGEST PIECES 

The goal to be attained in the most economical crushing and 
dividing is to crush the larger particles no more than necessary to 
prevent their one-sided composition affecting the accuracy of the 
results. The limiting size of particle is of course a constant depending 
on the nature of the material and the quantity of the lot. The earlier 
sampling mills in the western United States were strongly constrained 
to crush as little as possible, because the ore was desired coarse for 
blast furnace smelting. The combined considerations of economy 
"and preserving the ore coarse have given us most of the mill charac¬ 
teristics which are found in western samplers. The mills have been 
built and operated largely on an empirical basis, with thorough studies 
on the vital factors conspicuously absent. The limiting sizes for 


22 


MONTANA STATE BUREAU OF MINES AND METALLURGY 


different ores, minerals, and weights of lot is one of the studies on 
which comparatively little work has been done in a systematic way. 

In a general way, and as far as practicable, the present sampling 
mills are constructed to so crush the larger pieces that when a division 
is made there shall be no excessively large pieces. An excessively large 
piece is one which would materially affect the result, depending on 
whether it enters the sample or the reject. The mills are intended to 
make thousands of what may be termed the largest-sized pieces. A 
few of the larger pieces cannot, then, by getting in the wrong division, 
appreciably affect the result. 

Some investigators have supposed that the law' of averages would 
apply to the larger pieces in this way, that even if some excessively 
large and rich pieces should tend to increase the values in the samples 
there would be enough large lean pieces to conterbalance. Weldi, in 
1910, clearly demonstrated, by actual tests, that it is not admissible 
to use this interpretation of the probable distribution of results. A 
probability curve based on the average obtained by balancing a few 
large and individually important quantities would be much broader 
and flatter than the .curve indicated in Figure 5. 

The accuracy of the sampling operation is jeopardized in two ways 
by the presence of unsuitably large pieces; the presence of the piece 
affects the results, and it interferes with the work of the dividers. 
The common occurrence of pieces larger than intended is commented 
upon by Woodbridge^ in his paper on western sampling practice. 

In 1895, BruntonS published a paper containing an extensive dis¬ 
cussion on the safe size of the largest pieces for lots of ordinary ores 
and low-grade gold ores. Woodbridge^ gives a table, based partly on 
Brunton’s work and partly on experiments and practice, designating 
the smallest permissible w'eight of sample for different sized material. 
If it is necessary to have at least a certain amount of material for 
pieces of a given size, the converse statement must also hold, that if 
a lot of ore weighs only a given amount, then the largest pieces must 
have only the corresponding size. 


1 Weld, “Accurac}' in Sampling,” J. Ind. Eng. Cliem., Vol. 2 (1910), page 426. 

2 Woodbridge, T. R. ; ‘•Cre-Sampling Condition in the West.” U. S. Bureau of Mines, 

Technical Paper 86, page 57 (1916). 

8 Brimton, D. W. ; “The Theory and Practice of Ore-Sampling.” Trans. Am. Inst. Min. 
Engrs., Vol. XX\'., page 826 (1895). 

4 loc. cit. 


The table, as given by Woodliridge, follows: 




HIGH VALUE MINERALS 


23 


Smallest Permissible Weight of Sample 
for Varying Sizes of Crushing 


When Crushed To— 

Two inches . 

One and one-half inches.. 

One inch . 

Three-fourths of an inch. 

One-half inch ... 

Three-eighths of an inch. 

One-fourth inch .. 

Three-sixteenths of an inch 

One-eighth of an inch. 

Six-mesh ....i.. 

Ten-mesh . 

Eighteen-mesh . 

Thirty-mesh . 

Fifty-mesh . 


Smallest Permissible 
Weight, Pounds 

.10,000 

. 5,000 

.-. 2,000 

. 1,000 

. 400 

.. 300 

. 200 

.. 100 

. 75 

. 50 

. 25 

. 10 

. 4 

. 1 


Woodbridge applies the table tOi ordinary gold ores and suggests 
that the limits may be too restricted for low-grade silver ores. The 
relationships expressed in the table may well be adhered to for the 
sake of allowing a reasonable margin of safety. The common presence 
of ore pieces larger than the allowable size, frequently seen in Montana 
practice, is a condition which can be excused only because of the com¬ 
paratively low grade of the ores. 


HIGH VALUE MINERALS 

The influence of pieces of coarse gold in a lot of ore is so over¬ 
whelming as to make any table of quantity-size relationships of little 
value. Oxidized surface gold ores and quartz containing coarse gold 
are in places so rich that single pieces may easily vitiate the sample 
by whole ounces. Accurate sampling of such materials demands that 
the entire lot should be finely ground befo're dividing. It is usually 
admitted that ordinary sampling mills are not adapated to sampling 
ores contaning coarse gold; it is also obvious that it would not pay 
custom plants to install fine-grinding machinery for the small and 
infrequent lots of “spotty” ores. 

The prospector or miner who is getting out rich material and 
thinks he is not getting fair returns can install a small grinding 
machine and daily reduce to 20- or 40-mesh the few hundred pounds 
of ore he produces. A suitable grinder need not cost over $200.00, and 
with whatever power is available the small operator should be able 
to pulverize his high-grade ore so that any good method of sampling 
will give accurate results. 
















24 


MONTANA STATE BUREAU OF MINES AND METALLURGY 


EQUIPMENT FOR SAMPLING 

Several really difficult and obstinate conditions are met in the 
satisfactory execution of the principles of sampling, so that to do the 
work quickly, cheaply, and above criticism demands high engineering 
accomplishment. Modern precision and modern standards are always 
becoming more exacting, and although the last few years have brought 
few changes in the industry, there is yet opportunity for further work. 

CRUSHING AND GRINDING 

The following machines are about the only ones used in sampling 
plants to reduce the size of ore particles; 

a. Gyratory rock breakers—for the largest sizes. ■ 

b. Jaw crushers, Blake t3q3e—for large and medium sizes. 

c. Rolls—for intermediate and small sizes. 

d. Bell-type grinders—for small and finest sizes. 

e. Disk grinders—for the finest sizes. 

f. Bucking boards—for the finest sizes. 

Baby g 3 ^ratories and chipmunk crushers are now and then seen in 
laboratories, but their place is for special samples rather than for 
routine samples of large lots. 

The large crushers used in sampling works are alwa 3 ’'s commercial 
mill units. The practice is a great convenience to the sample mill 
designer, but, as already mentioned, the ordinary ore crushers are not 
perfect^' adapted to sampling, because it is possible for flat and 
rather large pieces to get through the crushers without suitable 
reduction. Single pieces entering a spring roll may be suitably 
crushed, but if several pieces enter together, or within a wave of fines, 
one or more pieces ma 3 " fail to be crushed because the rolls opened 
under the strain. 

The wear of the hard iron working surfaces is usually compensated 
b 3 " adjusting the opening, but the channeling of the jaws and the 
corrugation of roll shells takes place just as in any concentrating 
mill. As the sampling mills do not contain sizing and returning 
equipment unless for some additional function of the mill, it follows 
that samples frequentG^ contain pieces far too large for the size of 
the sample. 

The introduction of abraded iron into the sample during the fine 
grinding is a matter upon which data is apparently rather scanty. 
Fieldneri reports that the ash in five samples of coke was increased, 
on the average, 2.9% b 3 " grinding on a bucking board instead of in a 
pebble mill. The quartz used in the author’s mixing test contained 
onl 3 ^ 0.03% iron extractable from the small rounded grains, but 3.17% 
iron after grinding in the disk grinder. 


1 Fieldner. A. C. : “Notes on the Sampling and Analv’sis of Coal.” U. S. Bureau of 
Mines, Technical Paper 70, page 57 (1914). 



SPLIT SHOVEL S VMPLTNO 



FIG. «.—SPLIT SHOVEL, SA^IPLLVO. 


The .sample man is sliding 
is held in the poekets and 


the rejeet into pans; the sample 
will he piled and a;;;aiii divided. 










26 


MONTANA STATE BUREAU OF MINES AND METALLURGY 


DIVIDING INSTRUMENTS 

The Hand Shovel. —The division of a lot of ore into sample and 
reject by shoveling it over, and putting every fifth or tenth shovelful 
aside as the sample, is an old and useful method of sampling. The 
size of the pieces and the richness of the minerals must, of course, 
correspond with the lot size, while the restricted number of selections 
infers that the lot has received some mixing. 

There are evidently 1,000 selections made for sample if a 50-ton 
lot of ore is hand shoveled in 10-pound shovelfuls, and every tenth 
one is put to one side as the sample. As the size of the sample 
decreases the number of selections gets critically small, but is in a 
measure compensated for by the mixing. 

The method of shovel sampling is easily carried out if the material 
has to be moved by hand and is fine enough. Crushing must be intro¬ 
duced at the required stage if the material is not fine to start with. 
It is a common practice to shovel sample for the first, or first two 
divisions, and finish with the cone and quarter method. 

For nearly all large scale metallurgical work shovel sampling is 
far too slow and costly; the method also suffers because of the care¬ 
lessness of the workmen and because of an undesirable element of 
judgment in handling lots of mixed sizes. 

The Split Shovel .—The split shovel is in common use in some of 
the Montana sampling plants. It offers a convenient means of 
dividing a lot, but the number of independent cutting which can be 
made is small. It makes no difference how few selections are made 
if a lot of ore is well mixed, but in practice it is nearly always easier 
to make many cuts than it is to mix the ore. Figure 6 shows a sample 
man sliding the reject from a split shovel into discard pans. Material 
remaining in the closed pockets of the shovel will be piled and cut 
again. 

Riffle Cutters. —The widely-used Jones type of riffle sampler, built 
either as a floor stand or in table size, is a remarkable instrument for 
dividing and mixing ore samples. Suitable designs have from 16 to 40 
slots, are rigidly made, and have the slots wide enough to safely 
accommodate the particles poured over them. The ratio of 4 to 1 
is generally considered a safe one with which to express the “width 
of opening” over “diameter of particle” relationship. This ratio is 
usually greatly exceeded when riffling small sizes and is often far 
from being' attained when riffling coarse material. The instrument 
well deserves to Fe given both more variety in manufacture and more 
use in the industries. 

Figure 2 shows Jhe 26-slot stand cutter used at the Montana State 
School of Mines. Figure 7 shows a riffle with alternate bottoms 
closed, but as the cutter is fixed on a sharp slope it is a Jones riffle 
to all intents and purposes; this cutter is in use in several Montana 



TIiIn cutter Iium 10 sluts. A similar cutter Avitli ^tl> slots and half the slot width is more often useil 






28 


MONTANA STATE BUEEAU OF MINES AND METALLIIKGY 



l 


Plfi. s. —tOKNKR EAST HEEENA IIUCKIACi R003I, 

Biiekiiig^ hoards, scales, rillTes, cahinet dryer, sieves, and sample holders can he 

seen. 



PIPE SAMPLING 


29 


mills. Tn Figure 8 is seen a neat table riffle at the very left of the 
picture; this design is in use at the mills of the American Smelting & 
Refining Co. at East Helena, Montana. 

Pipe Samplers. —Pipe samplers have long been used in Montana 
and in other sections of the country, notably at the zinc mines in 
I\lissouri and Oklahoma, where the cars of concentrates are sampled 
with the “gun,” as the pipe sampler is there called, immediately after 
loading out for the smelters. Since the advent of flotation concen¬ 
trates, which are notoriously sticky and difficult to handle, pipe 
samplers have greatly increased in utility in the Butte district. 

Ore suitable for pipe sampling consists of concentrates or other 
fine material which has been produced in a regular and uniform 
manner, or has been mixed in handling. Flotaition concentrates may 
very in consistency from a thin mud to a dry powder. When sampling 
carloads of the muddy concentrates men are sometimes barely able 
to support themselves on the drying crust. Cars which have traveled 
long distances may have the load so firmly packed that an auger, 
rather than a pipe, is required to cut out the samples. 

According to the Montana practice, lots of concentrates are sampled 
at the mill by the shipper and later at the custom sampling plant, or 
smelter. Data as to agreement of assays is not available, but results 
are said to be wholly satisfactory. 

Pipe sampling of a carload of concentrates usually begins at one 
end of the car, where a row of holes two feet apart and two feet 
from the end wall is made; a parallel row is then punched two feet 
nearer the center and this is repeated until samples are taken in a 
systematic order over the entire length of the car from points about 
two feet apart. Hopper-bottomed cars have the two deep pits, which 
are hard to penetrate, but the pipes are long enough to touch the 
steel bottoms, as in the shallowed portions of the car. 

Pipes are commonly four to five feet long, three inches diameter 
at the top and two inches at the cutting edge. For firm materials, 
easily cleared, circular tubes are used; for sticky loads the pipe is 
slotted and provided with a scraper with which the sample man quickly 
forces the core out into the sample pan. A sample of 250 pounds 
weight is usually obtained by from 40 to 75 insertions of the pipe. 
Figure 9 shows three men sampling a car of flotation concentrates 
at the Washoe Sampler. 

Pipe sampling of the fine concentrates may continue in the bucking 
room until the final samples for moisture and assay are taken. The 
sample man merely goes over the pans of first sample with a smaller 
pipe, a foot long and an inch in diameter, and punches from all parts 
of the pans enough cores to give a sample of the required weight. 

The justification of pipe sampling clearly depends on the uni¬ 
formity of the lot of ore as it is spread in the .bin or car. To test the 
uniformity of a lot of concentrates in a railroad car, the author took 


30 


MONTANA STATE BUIJEAU OE ,MINES AND METALLURGY 



PIG. ».—PIPE SAI>IPIjI 1VG OP PGOTATIOJV PRODUCT, 
The pipes are of the slotted variety and eleaiied out with a s 









PIPE SAMPLING 


31 


40 four-ounce grab samples from the pipes as a car of flotation con¬ 
centrates was being sampled at a custom plant. Each of the samples 


was dried, 
results: 

, ground, mixed. 

and an 

alyzed for 

iron with 

the following 

Sample 

%Fe 

Sample 

%Fe 

Sample 

%Fe 

Sample 

%Fe 

1.... 

14.7 

11. 

...14.1 

21.. 

...13.4 

31. 

...14.8 

2. 

.14.2 

12. 

...14.8 

22. 

...15.5 

32. 

...16.2 

3.. 

.13.8 

13. 

...14.5 

23. 

...13.1 

33. 

...15.7 

4. 

.14.5 

14.... 

...13.8 

24.. 

...13.1 

34. 

...16.3 

5. 

.14.0 

15. 

...14.5 

25.. 

...13.1 

35. 

...17.2 

6... 

.14.2 

16. 

...14.1 

26.. 

...18.3 

36. 

...15.4 

7.. 

.14.3 

17.. 

...13.2 

27. 

...13.8 

37.. 

...14.8 

8. 

.14.1 

18. 

...13.6 

28.. 

...14.5 

38. 

...15.3 

9. 

.15.0 

19.. 

...12.8 

29. 

...14.8 

39. 

...17.4 

10. 

.13.0 

20. 

...15.0 

30... 

...15.0 

40.. 

...14.3 


The average of all the figures is 14.7%, and the average deviation 
of a single analysis is only .9% from the 14.7%. In other words, the 
average deviation from the mean is approximately 1 part in IS. From 
the sampling point of view it means that one could take a grab sample 
anywhere in the car and the probable analysis of that sample would 
be accurate to better than 1 part in 15. 

The main pipe samples, from which the little samples just discussed 
were ta.ken, weighed 25 to 30 times as much and were piled and again 
piped before drying, mixing, and grinding for the regular sample. The 
main sampling work might reasonably be expected to be 10' times as 
accurate as the author’s grab sampling, which would make the main 
pipe sampling accurate to more tham 1 part in 150, a precision consid¬ 
erably greater than ordinary assaying or wet chemical analysis. 

Pipe sampling of fine, mixed materials is very rapid and cheap; 
the test confirms the prevalent opinion that it is also accurate. 


The Brunton Vibratory Cutter. —One of the earliest sample cutters 
used in western sampling mills consists of a thin wedge of steel plates 
riveted to a shaft and set in the center of the ore stream as it flows 
from a spout. The thin wedge has the shaft inclosed along its base 
and points upward into the ore stream; by turning the wedge to one 
side or the other it deflects the entire ore stream first to one side, 
then to the other side; separate spouts catch the two ore streams 
made by the deflector. Spill is taken care of by steel wings on each 
side of the wedge or blade. The sample can be made any fraction of 
the lot by the relative periods the deflector remains pointing toward 
either sample or discard spout. Pins on a rotating disk engage a cam 
at the far end of the shaft and so throw the blade, first to one side, 
then to the other; by the adjustment of the pins in holes around the 
edge of the disk the periods are determined and the periods, in turn, 
determine the fraction selected for sample. 












































MONTANA STATE EUl^EAU OF MINES AND METALLUIIOV 


ti9. 



FIG. H>-Hill JVTOX \ IBKATORY CUTTER BLADES. 

Two sizes as used in one of the East Helena Sampling Mills. 



FIG. 11-MECHAAISM OF BRI NTOA OSt Il.LATORV SAMFLER. 

A erank arm on a disk ehanges the rotary motion of a pnlley to the oscil¬ 
lations of the eutter. 

(After Briinton, Trans. Am. Inst. Mi 


n. Engrs., 1909.) 















mu XTOX OSCILLATORY SVMPLKR 


33 



FIG. 12.—FIltST SAMPIiFR AXI) ROLLS AT THF WASHOK SAMPLER. 

The steel housing in front of the oseillator is tnriie<l down to expose the 
parts. The sample drops throiij^h the opening and falls to the rolls, the 
reject is deflected away to ji spout to the conveyor behind the rolls. 








MONTANA STATK BUKEAU OF MINES AND METALLUEGY 


Two sizes of Briinton vil^ratory cutter blades are seen in Figure 
10; they liappen to be spare parts for the machines now used in only 
one mill in Montana. 

The vibratory cutter slips through the ore stream quickly, which 
is always an advantage; the blade also cuts the stream in the same 
direction for sample. If the repeated cutting in the same direction is 
considered a disadvantage, it is eliminated in the Brunton oscillatory 
cutter, which is next described. The driving mechanism of the vibra¬ 
tory cutter would doubtless have been further perfected if the oscil¬ 
latory cutter had not been invented. 

The Brunton Oscillatory Cutter. —In the States of Colorado, iMon- 
tana, Nevada, and Utah are many sampling mills built after the Taylor 
and Brunton design and equipped with the Brunton “time-sampler”, 
or oscillatory cutter. The general scheme of the driving machanism 
is plain after studying Figure 11, while a cutter is seen in place in 
Figure 12. 

The cutter is of the general ■ intersecting saucer type, but the 
machine oscillates back and forth across- a 120'° arc and its cutting 
edges enter the ore stream first from one side, then from the other, 
instead of always from the same side. The small sample cut is plainly 
made by a division of the stream, the deflecting planes entering first 
from one side, then from the other. The division of the ore stream is 
smooth and clean-cut, while the driving mechanism is noiseless and 
lasting. The wearing parts of the oscillatory cutter are the edges of 
the sample segment and the floor of the larger reject casting; the 
small sample casting can be frequently renewed at slight expense, 
thus maintaining the cutting edges, while the larger casting is renewed 
as often as worn out. 

The East Butte Cutter. —Figure 13 illustrates the mechanical cutter 
used at the East Butte mill. It rotates in a horizontal plane and is 
obviously of the intersecting saucer type. The unit seen in Figure 13 
has 4 sample openings and would make a 20% selection, the units 
actually in place in the mill have 2 openings and make about 10% 
selections. The cutters are entirely suspended from above and the 
ore stream enters them either vertically or at a steep angle. 

The Vezin Cutter. —The Vezin type of mechanical cutter is made 
in several modifications of the original intersecting cone type. In all 
forms the lower cone, either real or imaginary, is extended upward 
on two opposite arcs in a sort of wing design; it is into- the rotating 
wings that the sample falls and is discharged through the restricted 
lower apex of the cone. It is well to compare this machine (Figure 
14) with the East Butte cutter and note that both are closely related; 
by merely altering the relative sizes of the parts, the sample or the 
discard is made to fall through the apex of the inverted cone. 


EAST BUTTE SAMI’LEI 


35 





ksIsMM 


FIG. la_EAST BUTTE TYPE OP SAMPLER. 

This cutter hs:s four slots; the cutters installed have only two slots. 







3(5 


MONTANA STATE BUREAU OF MINES AND MFITALLURGY 



The Snyder Sampler. —A slotted saucer, rotating on a horizonal 
axis, forms the base idea of the Snyder sampler. A sloping feed spout 
neatly directs the stream of ore through the inclined opening as the 
sample slot passes. The similarity to the several other intersecting 
saucer types is apparent from Figure 15. The machine usually has 
two sample lots, as seen in the picture, but the only unit known to be 
installed in Montana, which is a 28-inch machine in the ore-dressing 
laboratory of the State School of Mines, has a single slot. 


FIG. 14.—VKZIN SAMPLER. 

Several iHOrtifieations of the type are ii» eom- 
mon use. This is the design supplied by 
Traylor Eiig. & Mfg. Co. 


The actual amounts of sample cut by the various samplers is an 
important topic which has not been thoroughly investigated. The 
only data which the author has seen are figures obtained by the 
Anaconda Copper Mining Company. These figures indicate that, in 
their mills, considerably less than the expected amount is selected. 

The uniformity of the ore stream on entering the cutter-is a large 
factor in the constancy of the fraction cut for sample. The mixing 
and retarding drums at the East Butte mill give an exceptionally 
uniform feed to the cutters and the fraction cut out is reported to be 
practically constant. 












M 

I 



FKi. 15-TWO-SLOT SNYDER SA3IPI.ER. 

The saucer rotates In a vertical plane. 









1*1 


38 MONTANA STATI-: BUREAU OF MINES AND METALLURGY 

A careful inspection of the relative sizes of cutter openings and 
ore pieces shows that the ratio of 4 is not often attained in the case 
of the first cutters. It is believed that attention to this detail will add 
to the perfection of future mills. 

The number of cuts made by mechanical cutters is sometimes in¬ 
sufficient for accurate work, especially if the lot is hurried through 
the mill. The difficulty with speeding up cutters is the batting and 
scattering action on the larger pieces as the velocity of the machine 
increases. i\Iany cutter designs are already on the market, but, if it 
.should be found desirable to make more cuts in a unit time, it ma\ 
not be too much to expect an improved design for high speed work. 


MIXING MACHINES 

Henry A. Vezin is commonly credited with first having used mixing 
and retarding drums in large scale sampling operations. He placed 
staggered baffles in the drums to mix the ore before it fell in a steady 
stream to the cutter below. 

The mill of the East Butte Copper Mining Company, at Butte, 
Montana, has two mixing and retarding drums (see Figure 16) before 
the second and third cutters, respectively. Thus, as the first cutter is 
fed by the main ore stream, all three cutters are fed with a decidedly 
well-mixed and uniform stream of ore. 

The other Montana mills depend largely on shaking feeders to 
mix and spread the samples, which one cutter delivers to the next. A 
revolving disk is, however, found in the No. 2 mill at East Helena, 
between two Vezin cutters; this feeder gives an especially uniform 
feed to the lower Vezin. 

Retarding machines are highly desirable to elongate and equalize 
the ore stream after a cut has been made. Natural spreading in the 
short spouts does not give a smooth ore flow to either rolls or 
cutters. Syncbromatic gaps and irregular fractions are naturally 
greatest when the stream equalization is least. Aside from the equal¬ 
izing for rolls and cutter, any mixing of the material may be con¬ 
sidered an incidental matter if the number of selections by each 
machine amounts to more than a thousand, and the values in the 
large and rich pieces do' not exceed the limits for accuracy. The 
mixing of the ore stream is, however, an assurance of correct results 
if the number of cuts is reduced to only a few hundred. 

It may not be out of place here to analyze just what happens on 
mixing a small lot of ore with the riffle cutter. We will suppose that 
a lot is poured over a 30-slot riffle with 50 shakings to and fro, the two 
halves are then united and the pouring repeated; the entire operation 
of cutting and uniting is continued until it has been done 10 times. 

The slots divide the sample into 30x50, or 1,500 portions, at each 
pouring. The 1,500 portions are not superimposed but are spread out 
into 50 layers at each pouring; when the halves are joined the 50 
layers from each side get superimposed, or, as may be said, each 




FIG. 1(5.—Dill >[ 3IIAEK, SAMPLER, AND ROLI.S IN EAST IIUTTE MILL. 
This is (he upper (Iruni lui.ver, :iiu1 the No. 2 sampler over the No. 2 rolls 













40 


MONTANA STATE BUREAU OF MINES AND METALLURGY 


pouring puts the material in 100 layers when the halves are united. 
On repeating the work 10 times the material clearly gets divided into 
10x1,500 portions and the full num1)ers of layers increase to 10x100, 
or 1,000. The 100 layers made by the 1,500 portions at any one pouring 
give a splendid lateral distribution of any inequality, but cannot pos¬ 
sibly equalize throughout the pulp any segregation in either the first, 
middle, or last of the lot poured. But uniting the halves and repeating 
does effectually dispense the vertical segregation, as the inequalities 
in the first, middle, or last of the pouring may be called. Thus, with 
a few repetitions, the lot becomes uniform laterally and vertically, or 
is well mixed. The previously described test on the quartz and iron 
ore is very good proof of the efficiency of riffle mixing. 

DRYING MACHINES 

It has already been mentioned that the Montana practice uses both 
steam and electrically heated cabinet shelf-dryers, as well as large 
steam tables. In all cases the operation is very simple and requires 
no attention. Although drying requires about the same time as mill 
sampling, it is, nevertheless, so rapid and simple that there is little 
incentive to speed up the process. Faster drying would inevitably 
demand higher and injurious temperatures, as well as moving parts 
to the drying apparatus. If all other essential operations in sampling 
were in as satisfactory a status as that of drying it would be fortu¬ 
nate, indeed. 


SAMPLING OF TEST LOT BY STATE BUREAU 

The results of resamplings and check samplings have been pub¬ 
lished from time to time, but to test the matter of sampling more 
exhaustively and at the same time provide tangible evidence that the 
custom mills in Montana are doing satisfactory work, the State Bureau 
acquired the use of a lot of ore and l\tad it sampled at the three most 
important custom mills. 

The carload weighed a little over 50' tons, and was from a Montana 
mine which is producing a silver-lead ore of considerably greater 
value than the average of the Butte mines. The ore was run-of-mine 
product and, like many high sulphide ores, more than half of it con¬ 
sisted of rather fine to earthy material. At least a quarter of the 
material was in lumps over two inches in diameter, and the rest was 
intermediate. 

The minerals varied in size and texture from large pure grains to 
fine intimate mixtures. The mineral composition was, approximately: 

Quartz ...30% Arsenical tetrahedrite 

Pyrite .25% (gray copper ore) .15% 

Galena .....15% Zinc blende . 5% 

Other gangue minerals 


10 % 











STATE BUREAU TEST LOT 


41 


The lot typified IVIontana ore of the better sort, with commercial 
values in gold, silver, copper, and lead; an ore suitable for demon¬ 
strating the precision of sampling on customary and average materials. 

The lot of ore was sampled twice at the Washoe Sampler, resulting 
in two independent final pulps. The lot was sampled in the No. 1 
mill at East Helena, using the coarse by-pass; it was tenth-shovel 
sampled at East Helena, and then finally ground to pass the 2-mesh 
screens and again sampled in the No. 1 mill, this time in the ordinary 
way. The lot was sampled once at the East Butte mill while in the 
coarse condition, but duplicate portions were taken from the mill 
product before fine grinding. 

Six different samplings were thus made, giving seven pulps; three 
different types of mechanical cutters were used and once the lot was 
hand-sampled. The hand-sampling was first by the tenth-shovel 
method, and it was then coned and quartered until the final splitting 
for packets was made with a table riffle. 

The actual sampling time at the different mills varied; at the 
Washoe Sampler the lot required 20 and 30 minutes at each respective 
sampling; at the East Butte mill 50 minutes were required for the 
sampling; at East Helena fully 2 hours were taken each time the lot 
was run through the mill. 

The final sampling at East Helena, after crushing to half-inch size, 
afforded a good standard test, since the material was then all in small 
sizes, had undergone repeated dispersions and retardations in the 
mills, and was cut at least 3,500 times by each of the mill samplers. 

The lot was sampled in the presence of the author in each instance; 
no particular arrangements were made at the mills, nor was the 
sampling carried out in any way differently from the routine pro¬ 
cedure which the author has repeatedly observed when he has hap¬ 
pened into the mills. 

The seven final pulps were analyzed under as nearly identical con¬ 
ditions as possible in the State School of Mines laboratories. Lest too 
few results might involve deviations in the chemical work instead of in 
the sampling, the analyses were checked over from 6 to 8 times so as 
to furnish average figures for each component. Pulp inequalities, 
chemical influences, and manipulations all introduce deviations, which 
repeated analyses alone can eliminate so as to show the precision or 
lack of precision in the sampling. 


MONTANA STATE BUIJEAU OF MINES AND METALEFRCY 


•12 


The results of the analytical work follow: 



Silver, oz 

. Gold, oz. 

Lead, 

Copper, 

Iron, 

Insoluble, 

Sample 

per ton 

per ton 

per cent. 

l)er cent. 

per cent, per cent. 

A ... 

.37.8 

.21 

12.73 

1.74 

14.49 

32.58 

B ... 

.37.3 

.22 

12.46 

1.69 

14.43 

33.07 

C ... 

.37.0 

.23 

12.50 

1.74 

14.46 

32.87 

D ... 

.....37.9 

.21 

12.64 

1.78 

14.77 

32.01 

E ... 

.37.3 

.21 

12.64 

1.76 

14.52 

32.83 

F ... 

.37.4 

.21 

12.72 

1.70 

14.35 

32.50 

G ... 

.37.5 

.22 

12.91 

1.73 

14.72 

32.22 

One 

conclusion 

, only, can he drawn 

from th( 

i results 

in the table: 

namely, 

that the sampling was well done in each 

instance 

. The differ- 

ence between the 

several pulps is less 

than excellent an 

alysts might 

report on one and 

the same 

pulp. 




The 

individual 

items and 

gross values of the 

lot may i 

be calculated 

for each 

sampling, 

reckoning silver at $1.25 an ounce, gold at $20.67 an 

ounce, lead at 8 cents a pound, and copper at 18 

cents a 

pound. • 







Deviation 

Sample 

Silver 

Gold 

Lead 

Copper 

Total 

From Mean 

A ... 

.$47.25 

$4.34 

$20.37 

$6.26 

$78.22 

$0.44 

B ... 

. 46.62 

4.55 

19.94 

6.08 

77.20 

0.58 

C ... 

. 46.25 

4.75 

20.00 

6.26 

77.26 

0.52 

D ... 

..... 47.38 

4.34 

20.22 

6.41 

78.35 

0.57 

E - 

. 46.63 

4.34 

20.22 

6.34 

77.52 

0.26 

F .... 

. 46.75 

4.34 

20.35 

6.12 

77.56 

0.22 

G ... 

. 46.88 

■ 4.55 

20.66 

6.23 

78.32 

0.54 


The total values range from $77.20 to $78.35, an extreme difference 
of $1.15; the average deviation from the mean of all the totals is $0.45. 
Ore producers should certainly l)e well satisfied with custom sampling 
which shows this degree of precision. 

MILL FLOW SHEETS 

To indicate the treatment by which each of the samples was 
obtained in the State Bureau test, the following flow sheets have 
been prepared. 



















sVASHOK SAMPLER FLOM' SHEET 


4:^ 


Washoe Sampler— 

Cars unloaded over hopper; 18'x20'xir deep 

Shaking grizzly feeder; 1.5"x2.0" holes in 24"x20" section 

Crusher; 20"xl0" opening 

Shaking tray 

Elevator to top of mill 

No. 1 cutter; Brunton oscillatory, 7.0"xl0.5" opening, 40 cuts 
per minute 

Sample; 20%, or 20,000 lbs. on 50-ton lot 
Shaking tray; 12" effective length 
No 1 rolls; 16"x36" 

No 2 cutter; Brunton oscillatory, 6.0"x8.0" opening, 28 cuts per 
minute. 


Sample; 20%, or 4,000 lbs. on 50-ton lot 
Shaking tray; 9" effective length 
No. 2 rolls; 14"x30" 

No. 3 cutter; Brunton oscillatory, 4.5"x6.75" opening, 63 cuts per 
minute 


Sample; 20%, or 800 lbs. on 50-ton lot 

Bell distributor 

No. 3 rolls; 12" x 24" 

No 4 cutter; Brunton oscillatory, 3.5"x5.0" opening, 68 cuts per 
minute. 


Sample; 160 lbs. on 50-ton lot 
Trolley bucket 

Steel sampling floor in bucking room 
Split shovel to 8 to 10 lbs. 


Sample; 8 to 10 lbs. 

Dried in shelf cabinet, electric heat 

Engelbach grinder 

Riffle cutter; 26 slots, each .64"x2.0" 

Sample; 32 ounces 
Braun disk grinder 

Hand sieves; 100, 120, 150, and 200 mesh 
Rolled on pebble-surfaced oil cloth 1,000 times 
Sample split for 4 packets with inclined riffles 


44 


MONTANA STATE BUREAU OF MINES AND METALLURGY 


East Helena No. 1 Mill— 

Cars unloaded onto steel pan conveyor; pans 18"xl8"x6" 
Chute to No. 5 McCully gyratory crusher 
Belt conveyor, 16" belt, to top of mill, under magnet 
Chute to 

A (fine grinding and sampling) 

Trommels; 12'x60", ^"x->^" mesh 


over 

under 2-SGotion trommel, 

16» X 36" 

No. 1 cutter; Vezin, wings 14" and 
3"x20", 30 cuts per minute 

Sample; 20%, 20,000 lbs. on 50-ton 
lot 

Shaking tray; 4' effective length 
No. 2 cutter; Vezin, wings 7" and 
1.5"xl0", 34 cuts per minute 

Sample; 20%, 4,000 lbs. on 50-ton 
lot 

Shaking tray; 4 ' effective length 
Rolls; 12"xl2" 

Shaking tray; 4 ' effective length 
No. 3 cutter; Vezin, same as No. 2 
cutter, 40 cuts per minute 

Sample; 20%, 800 lbs. on 50-ton lot 
Shaking tray; 3' effective length 
No. 4 cutter; Vezin, same as No. 2 
cutter, 40 cuts per minute 

Sample; 20'%, 160 lbs., on 50-ton lot 
Locked sample hopper 

Sample; wheelbarrow to steel sample floor in or near bucking 
room 

Cone and quarter, or riffle cut, to 10 to 12 lbs. 

Dried in shelf cabinet or on steam table 
Bell grinder 

Hand sieves; 100, 120, and 150 mesh 
Table riffle to 24 ounces 
Rolled 15 minutes on special paper 
Sample split with table riffle to 4, 6-oz. packets 


I- 

5/8" X 8.6" 
rectangles 


8 * 

oirclee 


rolls, 
16" X 36" 


oversiB# 


rolls, 
16" X 36" 


No. 4 

MoCully 

gyratory 


return conveyor 
to top cf mill 

I 

trommel, 12’ 60"| 
3/8" X 3/8" screen 

I 

r---1 

throMh ovoraiae 

_» I_ 






















EAST BUTTE SAMPLING MILL 


45 


B (coarse sampling) 
No. 1 Vezin cutter 


Sample; 20% 

Return conveyor to top of mill 


Discard, out of mill on conveyor 


Chute to No. 2 trommel, 12'x60", mesh 


under 

No. 2 Vezin cutter 


2-section trommel and closed 
circuit, as above 


over 


Same as under A to finished sample 

East Butte Sampling Mill— 

Cars unloaded over mill hopper 
Shaking feeder 
Crusher; 12"x24" opening 
Spout to elevator 
Elevator to top of mill 

No. 1 cutter; East Butte, 8"xl2" openings, 28 cuts per minute 

Sample; 10%, 5 tons on 50-ton lot 
Shaking tray; 3' effective length 
No. 1 rolls; 16"x36" 

Drum mixer; 6'x2', 16 r.m.p. 

No. 2 cutter; East Butte, 6"x7.75" openings, 26 cuts per minute 
Sample; 10'%, 1,000 lbs. on 50'-ton lot 
Shaking tray; 3' effective length 
No 2 rolls; 10"x24" 

Drum mixer; 5'x23", 10 r.p.m. 

No. 3 cutter; East Butte, 4.5"x5.5" openings, 16 cuts per minute 

Sample; 10%, 100 lbs. on 50-ton lot 
Shaking tray; 3' effective length 
No. 3 rolls; 9"x9" 

Sample can 

Cast iron riffle cutter to 15 to 20 lbs. 

Sample; 15 to 20 lbs. to bucking room 
Riffle cutter to 8 to 10 lbs. 

Sample to shelf cabinet or table dryer 
Bell grinder 

Table riffle to 16 ounces 

Hand sieves, 100, 120 and 150-mesh 

Rolled on cloth 

Table riffle; split to 4, 4-oz. packets 




MONTANA STATE BUEEAU OF MINES AND METALLURGY 


SAMPLING MILLS IN MONTANA 

THE WASHOE SAMPLER 

The $150,000 steel-concrete custom ore sampling plant of the Ana¬ 
conda Mining Company is known as the Washoe Sampler and is 
situated on the main line of the Butte, Anaconda, and Pacific Railroad 
at Butte, Montana. The main mill portion is absolutely fireproof; it 
was put in operation in 1911, after a fire had destroyed the previous 
structure. The new mill was designed and built by the company engi¬ 
neers following the Taylor and Brunton system, which had been suc¬ 
cessfully demonstrated in the first mill. 

Figure 17 is a diagram of the Taylor and Brunton system, which, 
in a general way, is the scheme followed in the present sampler. The 
Brunton oscillatory time samplers are, of course, the cutters installed. 
The types of machines used and the fractions cut at the several stages 
have already been indicated in the flow sheet of the mill, and are 
repeated in Figure 17. The main machinery tower has floors 35 feet 
by 45 feet; the main elevator pit floor is 28 feet below the ground 
floor, and the ridge of the building is 68 feet above, a total elevation 
of 96 feet thus being used. 

The arrangement of the mechanical, power, and switching facilities 
is such that 500 tons of ore can be sampled in an 8-hour shift, and 
1,200 tons can be put through in 24 hours. A 50-ton lot has been 
sampled in 9 minutes, but the usual running time is from 20 to 30 
minutes; if ore comes in box cars the sampling depends on how long 
the unloading takes. 

Figure 18 shows a portion of the tracks serving the plant. After 
weighing on the upper set of Fairbanks TOO-ton recording beam scales, 
the cars are lowered by cable to the right hand side of the mill and 
unloaded in the shed over the mill hopper. As soon as a car is 
unloaded it can be pulled back with the electric hoist and let down 
on the left side of the mill to receive the same lot of ore it originally 
contained. On the loading side of the mill is a second scale; cars 
can thus be switched from one side of the mill to the other in a minute 
or two. They can be weighed after loading and then let down farther 
on the same track for delivery to the railroad. 

A wagon and truck unloading shed is seen at the right in Figure 
18; below the floor of the shed are fourteen 50-ton hoppers over a 
conve 3 mr which delivers to the mill hopper. The brick structure seen 
between the tracks in the foreground of Figure 18 houses the black¬ 
smith shop and change room. Figure 19 shows how massive cast iron 
pipe may be used for permanent and tight spouting in mill equipment. 

The mill normally selects 0.16% of the original lot for the bucking 
room; by using a special cam arrangement in the mechanism of the 
second cutter only 0.04% need be cut out. The smaller cut is conve¬ 
nient on large lots. Four cutters will be used on lots weighing between 



TAYLOH AND BRUNTON SAMRLINCJ SYSTEM 


47 


J5t Cut 

■ OO- Lb. Sample 
Prom 1 Tan 

PJo. i Sampler 
20% Sample 

Coarse 
Crushing JR oils 
/6x36 Rolls 
■No.S Sampler 
20°% Sample 

2 nd Cut 
» 30-Lb Sample 
Prom 1 Ton 

Pine 

Crushing Rolls 
MxZ7 Rolls 
3rd Cut 

■ IC-Lb. Sapnpie^ 
From 7 Ton 



/Vo J Sampler 
20 % Sample 
Sample Rolls 
i2x20 Rolls 
Line Shaft 
xith Cat 
* 3.2-Lh. Sample 
Prom J Ton 
0.62% Discard 
Safa 

0.16% Sample 

JVo. -2 Sampler 
20 7» Sample 

'■ 99.84jUyiScard 


FIG. 17.—TAYI.OR AND IIKl NTON SAMI»GING SVSTE3I. 
The Washoe Sampler follows this general <1 ingrain elosely. 

(After Brunton, Trans. Am. Inst. Min. Engrs., 1909) 














































































































































































































FIG. IS.—VIEW OF WASHOE SAMPLER FR03I THE EAST 













EAST HELENA SAMPLING MILLS 


49 


50 and 12.5 tons. Smaller lots require less cutters in the following 
gradations: on lots weighing from 25,000 pounds down to 5,000 pounds 
three cutters are used, on lots weighing from 5,000 pounds down to 
1,000 pounds two cutters are used, and on lots weighing less than 
1,000 pounds only one cutter is used. The 1 /40th of the entire lot, 
which must be held 30 days according to the Montana law, is usually 
the reject from the third cutter on large lots; with smaller lots it 
may be the reject from the fourth cutter or even the entire lot itself. 

The frontispiece shows that the whole front section of the mill 
is merely a row of 50-ton steel bins; these bins are, of course, avail¬ 
able for storing large lots whenever necessary. Beneath the large bins 
are 48 small bins on the ground floor of the mill, which are in con¬ 
tinual use for storing the ll/40th portions. When the legal period has 
elapsed, the reserve bins are emptied in groups and a composite lot is 
run through the mill and then sent to the smelter. Superintendent 
Margetts states that the reserve samples are very rarely called into 
service; whenever one is used particular attention is given to properly 
cutting down the entire sample in the presence of the shipper. The 
shipper is never allowed to take a small grab sample for control assay. 
When the reserve samples are properly worked down to the final 
packets, in the same manner as the original sample was, the assay 
results prectically always check the first assaying. Only in the rarest 
instances is a complaint carried further. 

The tendency to increase the fineness of grinding has been marked 
in the case of the Washoe bucking room. The 80-mesh sieve once 
used has been entirely discarded. Copper ores are ground to pass 
100-mesh, silver ores are ground to pass 120-mesh, high-silver ores, 
lead ores, and zinc ores are ground to pass 150-mesh, and high-gold 
ores to pass 200-mesh. The mill experience has been that lead and 
zinc ores, as well as the rich gold ores, require the finer grinding for 
satisfactor}' chemical results on the pulps. If gold metallics are 
encountered they are ground with some of the pulp on the bucking 
board until everything passes the screen. Local experience is that 
metallics in ores tributary to the Anaconda smeltery easily yield to 
disintegration when ground with sample pulp; after rolling on the 
cloth the metallics become uniformly dispersed throughout entire pulp. 

THE SAMPLING MILLS OF THE AMERICAN SMELTING & 
REFINING COMPANY AT EAST HELENA, MONTANA 

The American Smelting & Refining Company provides extensive 
sampling facilities for the custom ores which maintain its lead smeltery 
at East Helena, Montana. The smeltery started operations just 30 
years ago, and some of the sampling mill construction dates from 
about that time, although many improvements and large additions 
have been made meanwhile. The plant maintains three distinct 
sampling mills and a steel sampling floor, 55 feet by 65 feet in the 
clear, for cone and quarter sampling. 



50 


MONTANA STATE BUREAU OF MINES AND METALLURGY 



FIG. 10.—THIHD SAMPGFU AiVIl THIRD ROLLS IN WASHOE SA3IPLER 

This set of rolls luis the hell distributor inside the housing- over the rolls. 
I'he pipe sit the hsiek of the eutter ejirries reserve sample to the trolley 

hueket on the first floor. 





EAST HELENA SAMPLING MILLS 


51 


The East Helena practice largely demands grinding ores and flux 
to pass 3y8-incli mesh to meet the roasting requirements. The com¬ 
pany has, accordingly, fitted both the No. 1 and No. 2 sulphide mills 
to crush to this fineness and then to make the sample selections. The 
fine-grinding not only accounts for the peculiar flow sheet of the No. 1 
and No. 2 mills, but consolidates the cutters in small space and assures 
highly satisfactory mechanical division for sample. The No. 1 mill 
has provision for either grinding the entire lot to pass the 3/8-inch 
mesh trommels before sampling, or, after the preliminary crushing in 
the big gyratory, l|/5th of the lot may be cut out with the first sampler 
and then reduced to pass the 3/8-inch screen on its way to the last three 
samplers. The No. 2 mill is also for sulphide ores and furnace prod¬ 
ucts;/t has no by-passes in its closed circuit, which grinds to pass a 
5/16x3 /8-inch screen before sampling with two machines in close series. 
Both the No. 1 and No. 2 mills are provided with excellent models 
of the Vezin sampler. The No. 3 mill is for oxide ores and has Brunton 
vibratory cutters. The No. 1 mill delivers 1 /625th of the lot as sample; 
both of the other mills deliver 1 /25th of the lot as sample. 

The No. 1 mill is conspicuous in that it contains no elevators; the 
transfer and elevation of materials is entirely by conveyor, of which 
there are five in use. The steel pan conveyor, onto which all incoming 
ores are unloaded, is well indicated in Figure 20. It will be noticed 
that the conveyor rises at the far end; Figure 21 makes the nature of 
this rise apparent, for in this cut one sees that the conveyor enters the 
building which contains the No. 5 McCully gyratory. After passing 
the gyratory, the ore goes up the long incline to the top of the main 
mill building. The main building covers a space 63 by 30 feet; the 
structure is steel and concrete and houses the equipment which has 
been indicated in the flow sheet of the mill on page 44. Figure 22 
is a picture taken on the ground floor of the mill; the two 16x36-inch 
rolls and the No. 4 McCully gyratory are seen from left to right in 
the foreground, and the sample cabinet is farther back to the left. The 
first Vezin is on the second floor above the cabinet, and the three 
Vezin samplers following are in this cabinet on the ground floor. The 
two upper drawings of Figure 23 indicate the dimensions, the config¬ 
uration, and the spout approach to the Vezin samplers in the No. 1 
mill. The first Vezin makes 30 sample cuts a minute, the second 
makes 34 a minute, and the last two make 40 cuts a minute. 

The No. 2 mill is a massively-built wooden structure, with floor 
dimensions 63x36 feet, built to crush sulphide materials to pass 
5/16x3/8-inch rectangles before sampling with two Vezin samplers 
in tandem. After the mill feed passes the crusher, whose opening is 
9 by 15 inches, the material is elevated and dropped to a 14x27-inch 
set of rolls. The material is again raised and enters the trommel with 
5/16x3/8-inch openings, from which the undersize falls to the Vezin 
samplers and the oversize to a set of 14x26-inch rolls in a closed 
circuit with the trommel. The upper Vezin makes 35 sample cuts a 


MONTANA STATK JUREAT OF MINES AND METALLURGY 



FIG. 20.—UNLOADING OUE AT EAST HELENA NO. 1 AIILL. 


Steel pan eoiiveyor delivers to the No. 5 3IeC'ully gyratory in the shed 








NO. 1 MILL AT EAST HELENA 


53 



/f. 


Men nre niilondiiii; limestone fhsv onto the conveyor to the eonrse crnshinK shed. 








































51 


MONTANA STATE BUREAU OF MINES AND METALLURGY 



FIG. 23.—FIRST FLOOR EQUIPMENT AT EAST HELENA NO. 1 3IILL. 

I'lie Iliree-lioppertMl spouts from the trommel on the floor above lead oversize to the three large eriishiag units 

ill a row. The cutter cabinet is in the background at the left. 










VEZIN CUTTERS AT EAST HELENA 


.55 




FIG. 2.5.—AKZIN SAMPLER AVIXGS AT EAST HELENA SAMPLING MILLS. 

The two upper drawiiis's are of the cutter wings in the No. 1 mill; the two 
lower drawings are of the wings of the tandem cntters in the No. 2 mill. 
The measurements were taken from the machines and show' satisf;ictory design. 










50 


MONTANA STATE BUREAU OF MINES AND METALLURGY 



FIG. 24-STFEL. SAIIPGING FGOOR AT EAST HELt^NA. 

A platform scale is near the door; quartering- crosses and reserve sample bins are along the walls. 









EAST BUTTE SAMPLING MILL 


57 


minute and discharges onto a slowl}’^ rotating circular plate feeder, 
which pushes out a uniform stream to the Vezin below. The second 
Vezin makes 60 sample cuts a minute. 

The oxide, or No. 3 sample mill, is a small machinery tower at 
one side of the large steel sampling floor adjacent to the No. 2 sample 
mill. The oxide mill is provided with two jaw crushers, a set of rolls 
and No. 2 and No. 3 Brunton vibratory cutters. One-fifth of the 
original lot is delivered as sample. 

The steel sampling floor has a set of platform scales, a 10x7-inch 
crusher and a 12xl2-inch rolls. Screens are provided for breaking up 
lumpy ores and numerous crosses allow several hand-sampling oper¬ 
ations to take place simultaneously. Figure 24 is a view along one 
side of the steel floor; a cone of ore covered with canvas is in the 
foreground, wooden crosses are along the wall, while around the 
entire room is a row of covered bins to store the reserve samples. 
The mills are provided with 58 wooden reserve bins similar to those in 
Figure 24, and near the No. 1 mill is a group of 42 steel pockets for 
the same purpose. 

The East Helena mills are provided with commodious fine-grinding 
and finishing facilities. The bucking room is 27x57 feet; it has an all- 
steel floor and the following pieces of equipment; 

One Sturtevant, 3"x8", roll jaw crusher 

One F. M. Davis, 12"x20", rolls 

Two steam drying tables, each 30"x72" 

Two Engelhach type, fine grinders 

Three steel bucking boards 

One round steel table, 5' diameter 

One cabinet shelf dryer, 12 double shelves 

Two stand riffle cutters, 26, 5y8" slots each 

Two table riffle cutters, 36, 5yl6" slots each. 

The bucking room, as well as each of the mills, is, of course, pro¬ 
vided with pressure air for cleaning. Ores are commonly ground to 
pass 100-mesh, high-silver ores to pass 120-mesh, and gold ores to 
pass 150-mesh. Ground and sieved samples are rolled on a special 
black surfaced paper before cutting for the final packets with a table 
riffle. 

THE EAST BUTTE COPPER MINING COMPANY’S 

SAMPLING MILL 

The East Butte Copper Mining Company samples all of its second- 
class ore and custom ore in a mill adjacent to its smeltery at Butte, 
ATontana. 

The mill building is a wooden structure some four stories high, 
with a main sampling section 33 feet long and 18 feet wide. The 
crusher is under the hopper, over which the elevated track passes 
beside the mill. The crushed ore is elevated to the first sampler, 


MOXTANA STATE BUREAU OF MINES AND METALLURGY 


iK'' 



FIG. 25.—EAST BUTTE SAMPLING 3IILU. 

Lots of ore are reeeivert over the “high line” Jihove the bins to the left. Outgoing 
cars may he loaded on the receiving line or from pockets over the depressed 

track at the right. 

















SAMPLER AND ROLLS IN EAST BUTTE MILL 


59 



FIG. 2(;._THIUD SA31PL,KR AND THIRD ROL.DS IN FAST RIITTE SAMPL.FR. 

The sample esin is plaeert direetly iiiuler the rolls. Notiee the vertieal spout to the sample saucer, and the 

loiij^- shakiii;^- trough from the sampler to the rolls. 




GO 


MONTANA STATE BUREAU OF MINES AND METALLURGY 


which is in the top of the mill over the bin section which adjoins 
the main machinery section of the structure. A conveyor over the 
bins extends along the more elevated part of the building and allows 
sampled ore to be dropped in any one of the series of bins, to be sent 
back to cars on the high unloading line, or to be screened, and 
crushed, and dropped in special bins. Figure 25 shows the main 
machinery sections in the center of the picture; behind and to the 
right is the bin compartment, which is a story higher and has the 
series of spouts to load cars on the depressed track. The unloading 
line and mill hopper are under the roof at the left of the picture. 

The cutters used in the mill have already been described as the 
East Butte type, and the mill flow sheet has been indicated on page 
45. The large cast iron stand cutter used to finish the mill samples 
ready for the bucking room, is a prominent piece of equipment; it is 
the largest and most substantial riffle cutter in use at any of the 
sampling mills. Figure 16 gives an excellent idea of the drum mixers 
and the way they are placed over the samplers. The final sampler is 
pictured in Figure 26, where it is seen suspended between the spout 
from the last drum mixer and the shaking trough feeding the last 
set of rolls. 

A peculiar method is used in this mill for handling the sampler 
rejects. The reject from the first sampler, which is in the top of the 
mill under the dump of the single elevator, is run to final disposal as 
the lot is sampled. The rejects from the second and third cutters drop 
to a hoppered bin under the first floor, from whence, after the entire 
lot is sampled, they are conveyed to the elevator and follow the rest 
of the lot to its final disposal. 

Compressed air is used for cleaning. The bucking room contains 
the usual equipment for fine grinding, drying, mixing, and dividing. 

THE SAMPLING MILLS AT ANACONDA, MONTANA 

The Anaconda Copper Mining Company maintains two sampling 
mills in its great smeltery at Anaconda, Montana. The mills are 
almost exclusively used for sampling ores from its own mines, since 
custom ores are sampled in the Washoe Sampler at Butte. 

Figure 27 shows the huge main double sampler. It is probably the 
largest sampling mill in the world, having an 8-hour capacity of 2,000 
tons. The mill is constructed and operated in two entirely independent 
but identical units. ]\Iost of the ore handled comes from the Butte 
mines and averages about 3.2% copper, 2.5 ozs. silver, and 0.01 oz. 
gold. As the ore runs fairly uniform, the cut-offs between lots are 
indistinct, and the cleaning of equipment between lots, which is a 
ver}' important feature in all the other mills, is dispensed with. 

The Anaconda mill is of frame construction, with a sprinkler 
.system for fire protection. The floor section is 45 feet by 63 feet; 
there are four floors and a small liasement under the crushers. The 
general mill scheme is given in Figure 28, which correctly represents 


ANACONDA SAMPLING MILL 


61 



FIC 


A. C. Co 

















MONTANA STATE BUREAU OF MINES AND METALLURGY 



FIG. 2S.—DIAGRAM OF ANACONDA SAAII’LING 3IIDD. 

(Courtesy of A. C. M. Co.) 

The uppermost elevators now deliver to conveyors carrying to 

bins across the tracks. 


















































































































































































































SAMPLER AND CRUSHER IN ANACONDA MILL 


63 



FltU 20.—FIKST SAMFUFH 


AND SEC'OAD 


CHISHFR I-V ANACONDA 


The sampler is placed close to the crusher, 
eter of nearly siv feet, which muKes it h> 

the State. 


The oscillator has a diam- 
far the largest cutter in 





C4 


MONTANA STATE BUREAU OF MINES AND METALLURGY 


all but the more recent conveyors from the top of the mill across 
the tracks to the spouts delivering to the concentrator feed bins. 

The equipment is characterized by its large size and close spacing 
of cutters over the next lower crushing machine. The latter feature is 
well indicated in Figure 29, which shows one of the first Bruntons 
over its 8xl8-inch crusher. The mill also has a partial dust-collecting 
system with suction intakes at the most dusty points, and a cyclone 
separator outside the building. 

The bucking room is equipped with the following units in duplicate: 

Engelbach grinders Table riffles; 16 slot 

Braun disk grinders Power (air) screens 

Bucking boards Cube mixers; 8" sides 

Stand cutters; 26 slot 

Figure 30 is a splendid picture of the bucking room and its equip¬ 
ment. A 15-horsepower motor drives the equipment, while another 
small motor in the far corner is coupled to a fan which exhausts the 
hood above the two Engelbach grinders and delivers the dust outside 
of the building. The room beyond, which is just through the double 
doors seen in Figure 30, contains the steel floor for split shovel work, 
a 10 by 4-inch jaw crusher, moisture scales, and a large steam drying 
cabinet. 

The Southern Cross sampling mill is a plant addition made to the 
smeltery some three years ago by the company. The mill covers an 
area 25 by 48 feet, and has four floor levels; it is placed between two 
columns and under the “high line,” which tracks lead to the main 
sampling mill and the concentrator bins. The mill has been used only 
for sampling Southern Cross gold ore, which was not conveniently 
sampled in any other way. 

The crushing of the ore is done entirely b\^ jaw crushers. The 
cutters are of special design; they have a wing much like the Vezin 
wing, but oscillate back and forth in a horizontal plane by means of 
a gear-and-crank mechanism. 

The Southern Cross mill is sprinklered for fire protection; it is 
cleaned with compressed air, as other mills. It has its own bucking 
room equipped much as the larger Anaconda mill, but with single units. 


ANACONDA BUCKING ROOM 


65 



FIG. 30.—BUCKING ROOM AT ANACONDA SAMPLING MILL. 

The duplicate and orderly arrangement of the equipment is prominent. The air-driven shaking sieves are on the beneh at the 

right, the cube mixers are on the wall oxer the bench. 

—Photograph by Baker, A. C. M. Co. 














MONTANA STATE BUREAU OF MINES AND METALLURGY 


Gti 


Flow Sheet of the Anaconda 
Sampling Mill— 

Cars clump into bins under “high line” 

Collecting car under bins supplies two 50-ton mill hoppers 

Shaking trays 

Jaw crushers; 12"x24" 

Conveyors to elevators 
Elevated to top of 4th floor 

No 1 cutter; Brunton oscillatory, ll"xl5" openings, 24 cuts per 
minute 

Sample; 20% 

Jaw crushers; 8"xl8" 

No 2 cutters; Brunton oscillatory, 7"xll" openings, 36 cuts per 
minute 

Sample; 20% 

Shaking trays 
No. 1 rolls; 15"x40" 

No. 3 cutter; Brunton oscillatory, 5.5"x8" openings, 44 cuts per 
minute 

Sample; 20% 

Distributing boxes 
No. 2 rolls; 14"x26" 

No. 4 cutters; Brunton oscillatory, 3.5"x5" openings, 76 cuts per 
minute 

Sample; 20% 

Trolley bucket or wheelbarrow to steel floor 

Brunton split shovels 

Sample 

Steam cabinet dryers 
Engelljach grinders 
Stand cutters; 26-slot 
Sample 

Disk grinders 
Mechanical sieves (air) 

Cube mixers 
Table riffles; 16-slot 
Sealed packets 


SAMPLING IN CONCENTRATING AND CYANIDING MILLS 


G7 


SAMPLING IN MONTANA CONCENTRATING 
AND CYANIDING MILLS 

A great deal of sampling is done as part of the daily routine in all 
concentrating and cyaniding mills. In ore treatment plants condi¬ 
tions are decidedly favorable for cheap and accurate work. The 
greatest difficulty is unquestionably in the sampling of mill heads 
where hardly less than a full observance of all the rules for crushing 
and dividing can be expected to supply precise data. 

Every tenth car of ore for the great Anaconda 17,000-ton con¬ 
centrator is sampled in the Anaconda sampling mill which has already 
been described. All the ore going to the East Butte concentrator is 
sampled in the East Butte sampling mill, also one of the mills de¬ 
scribed in this paper. The Butte and Superior concentrator feed is 
hand sampled every half hour; 50 pounds are taken at each interval. 
The Timber Butte concentrator is equipped with a hand operated 
device which cuts out samples from the crushed feed as the stock 
pours from one conveyor head to another conveyor. The Shannon 
mine of the Barnes King Company is equipped with mechanical con¬ 
trivances which automatically cut out portions of the ore at the tram¬ 
way loading station; the sample is worked down to final pulp in the 
customary way. 

The sampling of the different streams of mill pulp is carried out 
in different degrees by various means in the several mills. Usually 
hand samples are taken at designated intervals. Swinging stream 
samplers are built in a variety of models and frequently used. com¬ 
plete automatic stream sampling system is in use at the Butte and 
Superior mill; an electrical timing and operating installation swings 
samplers across a half-dozen streams at exactly 8-minute intervals. 
Milling work inevitably smooths out inequalities in the raw ore; the 
material is abundantly crushed; mixings and dispersions occur 
throughout the line of pulp flow. The required precision of the 
sampling operation is obtained with slight expense for installation, 
upkeep, or attendance. 

Mill products can be sampled as pulps while the concentrates are 
flowing to collecting bins; they can be pipe-sampled as lots in bins 
or in railroad cars, or they can be hand-sampled by shovel and cone 
and quarter methods. 

As a rule, ordinary mill sampling, except for the sampling of the 
heads, is far easier to accomplish than the sampling of lots of custom 
ore; mill heads require practically the same treatment that lots get in 
the best of custom samplers. 


MONTANA STATE BUREAU OF MINES AND METALLURGY 


es 


SUMMARY AND CONCLUSIONS 

The principles involved in ore sampling have been more or less 
expressed by several writers, but no thoroughly adequate and mathe¬ 
matical treatment has yet been given. The present paper attempts to 
analyze sampling methods with the theory of probability and the 
distribution of results strongly in mind, although a mathematical 
treatment is not attempted. A lot of ore is a very complex aggregate, 
and to the sampling deviations are added those of chemical analysis; 
constants in an equation of errors, or for qualifying Woodbridge’s 
table of size-weight relationship. 

The equipment for ore sampling which is described in these pages 
is only that equipment found in actual use in Montana at the present 
time; the range of the types is wide but by no means includes excel¬ 
lent machines in use elsewhere. 

The figures given in connection with the descriptions of riffle 
mixing and pipe sampling may give a better insight into the character 
of those two operations. 

Sampling is now carried on extensively in Montana in seven 
sampling mills and in at least five large and important ore-dressing 
mills. It has been attempted to outline the procedure used in the 
different sampling mills, but a full account of the sampling in the 
twelve places would require a much larger bulletin than this can 
presume to be. 

Although sampling of ores and mill pulps is a perfectly practical 
and common operation, certain features are clearly open to change 
and improvement. The more obvious possibilities group about pre¬ 
cision, cost, efficiency, fire risk, safety, welfare, and hygiene. There 
always lurks the suspicion that, for the work done, and the end 
attained, present plants are extravagant in elevations, size of buildings, 
and general capital outlay for equipment and attendance. Montana 
sampling mills rank high in most of their technical features, with 
certain attentions toward improvement in conditions of safety, welfare, 
and hygiene they would probably become the most advanced types in 
their field of technology. 

The excellent results obtained by the State Bureau on the different 
samplings of the 50-ton lot of ore demonstrate the precision of the 
mills and the satisfaction and usefulness of mechanical sampling. 


IMPOKTANT PUBLICATIONS ON SAMPLING 


69 


'.IMPORTANT PUBLICATIONS ON SAMPLING 

1884—Briinton, D. W. “A New System of Ore-Sampling.” Trans. 
Am. Tnst. Min. Engrs., Vol 13, p. 639. 

Briinton’s first vibratory cutter is described. 

1895—Brunton, D. W. “The Theory and Practice of Ore-Sampling.” 
Trans. Am. Tnst. Min. Engrs., Vol. 25, p. 826. 

An extended study of the influence of large particles and 
rich minerals on the precision of sampling. Demonstrates 
the necessity for crushing between successive divisions. 

1898—llofman, H. O. “The Metallurgy of I^ead.” Hill Publishing Co., 
New York, 5th Ed., 9th Imp. 

Chapter 5 is a lengthy discussion of hand and mechanical 
ore sampling. 

1902—Johnson, Paul. “An Automatic System of Sampling.” Eng. & 
Min. J., Vol. 73, p. 514. 

Describes mill at Greenwood, B. C., with cuts and results. 

1908—Argali, Philip. “Machine Sampling.” Eng. & Min. J., Vol. 
86, p. 291. 

Refutes statement that retardation causes error in sampling. 

1908— Woodbridge, T. R. “Sampling by Machine.” Eng. & Min. J., 
Vol. 86, p. 917. 

Discusses mechanical sampling with data. 

1909— Bailey, E. G. “Accuracy in Sampling Coal.” J. Tnd. Eng. Chem., 
Vol. I., p. 161. 

Discusses probability curves involving large errors. 

1909 _Richards. Robert H. “Ore Dressing.” McGraw-Hill Book Co., 

New York. Vol. III., pps. 1570-1578. 

Principles and practice of sampling are discussed. 

1909_Brunton, D. W. “Modern Practice of Ore-Sampling.” Trans. 
Am. Inst. Min. Engrs., Vol. 40, p. 567. 

The Taylor and Brunton system is explained. Brunton’s 
oscillatory cutter is described. 

1909—Woodbridge, T. R. “Sampling by Machine.” Eng. & Min. J., 
Vol. 87, p. 269. 

Discusses mechanical sampling with data. 

1910 _Weld, Fred C. “Accuracy in Sampling.” J. Ind. Eng. Chem., 

Vol. 2, p. 426. 

Discusses application of probability curves to sampling. 

191(>_Huntoon, Louis D. “Accuracy of Mechanical and Riffle Ore 
Samplers.” Eng. & Min. J., Vol. 90, p. 62. 

Gives screen analyses and assays after riffle dividing. 


70 


MONTANA STATE BUREAU OF MINES AND METALLURGY 


1916—Woodbridge, T. R. “Ore Sampling Conditions in the West.” 
U. S. Bureau of Mines, Technical Paper 86. 

An excellent study of the more important aspects of hand 
and mechanical sampling. A general summary of western 
practice is given as well as flow sheets of the mills. 

1919—Rice, Claude T. “Sampling Practice at Independence Mill.” 
Eng. & Min. J., Vol. 107, p. 641. 

Describes the Coard mixer and divider for final pulps. 



INDEX 


71 


INDEX • 


A. 

Page 

Abraded iron .12 24 

Acknowledgments .’ 7 

Anaconda— 

bucking room . 64 

flow sheet . 66 

sampling mills .60, 61, 62, 63, 64 

Analyses— 

Bureau test lot. 42 

flotation car . 31 

lead bullion . 11 

mixing test . 15 

Authorization . 7 

B. 


Brunton— 


on large pieces. 

oscillatorv cutter. 




22 

32, 33, 

34, 

43, 

46, 

64 

vibratory cutter . 

..31, 

QO 

0 

57 

Bucking rooms— 

Anaconda ... 




64 

East Butte . 




60 

East Helena __ 




57 

Washoe . 




49 

Bureau test lot. 


.40 

,41, 

42 

C. 

Cabinet dryers . 



-17, 

40 

Cloths for rolling. 




13 

Concentrating mills in Montana.. 


66 

Conclusions . 




68 

Cone and quartering_ 


-17, 

18, 

19 

Cost of sampling. 


8 

Crosses for sampling.... 



.19, 

56 

Crushers .. 



24 

Crushing—- 

economical . 




21 

machinery ...... 



11, 

24 

operation .. 



- 9, 

11 

surfaces . 



.12, 

24 

Cube mixers . 



.13. 

64 

Cutters— 

Brunton .31, 32, 

33, 

34, 

43, 

66 

East Butte . 



.34, 

39 

riffle . 



13 

Snyder . 



-36, 

37 

Vezin . 

.34, 

36, 

51, 

55 

Ciitting . 

...9, 

12, 

14, 

15 


Page 

Equiprnent for sampling. 24 

Essential operations of sami^ling. 9 


F. 

Fabrics for mixing... 13 

Fieldner on abraded iron... 24 

Pine grinding ...24, 49 

Pines in crushing.......’ n 


Flow Sheets— 

Anaconda . 66 

East Butte .. 45 

East Helena . 44 

Washoe . 43 

G. 

Grab sampling flotation car. 31 

Grinder for prospectors. 23 

Grinding (see crushing) — 

coarse gold . 49 

substance ...12, 24 

“Gun” sampler . 29 

H. 

Hand shovel sampling... 26 

High value minerals. 23 

I. 

Impartial sampling . 12 

Influences in sampling. 19 

Iron— 

in mixing test. 15 

in samples . 24 

J- 

Jones riffle . 26 

L, 

Large pieces .11, 12, 21, 22 

Law of averages .19, 22 

Lead sampling . 10 

Literature on sampling.69, 70 


M. 


D. 


Definition of sampling. 9 

Dividing—- 

lots . 9, 12, 19 

instruments . 26 

Drum mixers . 38, 39 

Dryers . 17, 40 

Drying samples ... 9, 17, 40 

E. 

East Butte— 

cutter ....34, 35 

flow sheet . 45 

mixers .-. 38 

sampling mill . 57, 58 

East Helena— 

flow sheet . 44 

hiffles .-.-.-. 26 

sampling mills.49, 51, 53 


Mechanical sampling 




12 

speed . 




12 

cheapness . 




12 

Methods of sampling 




10 

Mills, sampling— 

Anaconda . 

60, 

61, 62, 

63, 

64 

East Butte . 


..57, 58, 

59, 

60 

East Helena . 


. 49,51 

Washoe . 

43, 

46, 47, 

48, 

49 

Minerals, high value.. 



23 

Mixing— 

by ringing . 




19 

drums . 



.36, 

38 

necessity .. 



. 9, 

13 

samples .. 

..9, 

12, 13, 

15, 

38 

test .-. 




15 

Moisture sample .. 




17 

Montana— 

concentrating mills 




67 

reserve sample law. 




49 

sampling mills . 




46 

































































































72 


MONTANA STATE BUREAU OF MINES AND METALLURGY 


INDEX— Contimied 


N. 


Number of cuts..10, 12, 15, 

O. 

Object of bulletin. 

Operations of sampling. 

P. 

Permissible weights . 

Pipe sampling . 

Precision in sampling. 

8 , 12, 17, 19, 

Principles of sampling. 

Probability— 

curve . 

sampling . 

Pulp mixing . 

Purpose of sampling. 

R. 


Reserve samples . 

Results— 

of sampling lead. 

on test lot. 

Retarding drums . 

Riffles .12, 13, 

Ringing the cone. 

Rolling samples . 


S. 


Page 
19, 21, 26 

. 7 

. 9, 21 


23 

11^ ‘29, 30 


Page 

mixing .9, 12, 13, 15, 17, 38 

molten lead . 10 

necessity . 9 

operations . 9 

pipe .11, 29 

precision . 8 , 12 

principles . 9 

probability . 12, 19 

publications .69, 70 

purpose .-. 8 

sequence in . 10 

test lot . 40 


21, 31, 42 time .. 8 

. 9, 19 School of Mines— 

riffle ..13, 26 

.21, 22 Snyder disk . 36 

.12, 13, 19 Segregation .13, 19 

. 13 Selecting sample . 9, 12 

. 8 Sequence in sampling. 10 

Sieves .43, 44, 45, 49 , 

Snyder sampler .36, 37 

Southern Cross mill. 64 

..49, 57 Split shovels .25, 26 

Spotty ores . 23 

. 11 State Bureau— 

. 42 authorization .:.. 7 

.36, 38 staff . 4 

17, 27, 28 test lot ...40, 41 

. 19 Summary . 68 

. 13 


T. 


Sample— 

cloths . 13 

division . 12 , 26 

drying . 9, 17 

mixing .;.12, 13 

Weights ... 23 

Sampler— 

Anaconda .12, 34 

Brunton .31, 32, 33, 34 

East Butte.34, 45, 57, 58, 59, 60 

East Helena.49, 51, 53, 54, 57 

Snyder .36, 37 

Vezin .34, 35, 51, 55 

Washoe . 46 

Sampling— 

accuracy of . 8 

at Anaconda . 67 

at Barnes King. 67 

at Butte and Superior. 67 

at East Butte. 67 

at Timber Butte. 67 

cost . 8 

cone and quarter. 17 

crosses . 19 

defined . 9 

equipment . 24 

for moisture . 17 

impartial . 12 

in West . 10 

influences . 19 

mills in Montana. 46 


Tal)le riffles . . 13 

Taylor and Brunton System.46, 47 

Test— 

of mixing .15, 17 

of uniformity . 17 

of sampling. 8 , 9, 29, 31, 40, 41 

Theory of prol)ability. 19 

Time of sampling. 8 , 41 

U. 

Uniformity test . 17 

V. 

Vezin sample cutters.34, 35, 51, 55 


mixing drum . 38 

W. 

• 

Washoe sampler— 

bucking room . 49 

description . 46 

flow sheet . 43 

Weights of sample.23, 36 

Weld on sampling... 22 

Western sampling.10, 21 

Woodbridge—■ 

on large pieces... 22 

principles of sampling. 9 

table of safe weights. 23 




























































































aurre m(ner co., printers 






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